Cooled RF Probes

ABSTRACT

An electrosurgical device is provided that includes a probe extending in a longitudinal direction and having a proximal region and a distal region. An inner diameter of the probe defines a lumen. The probe has an electrically insulated portion extending from the proximal region to the distal region and an electrically exposed conductive portion located at the distal region. The electrically exposed conductive portion delivers radiofrequency energy to an area of tissue adjacent the distal region. The device also includes a heat transfer system for removing thermal energy from the area of tissue that is in thermal contact with the area of tissue. The heat transfer system removes from about 0.1 Watts to about 50 Watts of energy from the tissue. In addition, the heat transfer system can sufficiently draw heat away from the tissue without the use of a peristaltic pump for circulating a liquid inside the lumen.

RELATED APPLICATION

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 62/403,876, filed on Oct. 4, 2016, which isincorporated herein in its entirety by reference thereto.

FIELD OF THE INVENTION

The present invention relates generally to electrosurgical devices andmethods for the treatment of pain.

BACKGROUND

Electrosurgical procedures typically rely on the application of highfrequency, for example radiofrequency (RF), energy to treat, cut, ablateor coagulate tissue structures such as, for example, neural tissue at aspecific target site such as a lesion. The high frequency energy isoften delivered to a region of tissue from an energy source such as agenerator via an active electrode of a probe that is inserted into apatient's body via an introducer. The resistance of tissue that islocated proximate the active electrode of the probe to the highfrequency energy causes the tissue temperature to rise. If thetemperature is increased past a certain tissue-dependent level, referredto as the lesioning temperature, tissue damage will occur, and a lesionwill form. Often, the tissue proximate to the probe heats up faster thantissue farther away from the probe, and tissue carbonization and liquidvaporization may occur, all of which may limit the size of the lesionand thus the effectiveness of the treatment. Thus, in order to extendthe size of a lesion, the RF treatment may be applied in conjunctionwith a cooling mechanism. By cooling the probe, the tissue temperaturenear the probe is moderately controlled. In turn, tissue carbonizationand liquid vaporization is minimized, and more power can be applied tothe target tissue, resulting in larger lesions and improved physicianflexibility.

Several RF probes utilize cooling mechanisms that include a peristalticpump that distributes coolant water through tubing inside the probe,where the coolant water then absorbs heat from the active electrode tipof the probe through convection. This configuration has addressed issueswith carbonization and lesion size, but the pump and the extra tubingtake up valuable space during procedures. In addition, when filled withwater, the tubing weighs down on the probe and can result in movement ofthe probe during procedures, which is not ideal. Such movement disruptsthe tissue-probe interface, and oftentimes the physician will need toreposition the probe, exposing the patient and physician to extraradiation since fluoroscopy is used to position the probe.

In light of the above, a need currently exists for an electrosurgicaldevice that includes a cooling mechanism that is more patient andphysician friendly that does not require repositioning and theunnecessary exposure to additional radiation that coincides with suchrepositioning.

SUMMARY

In accordance with one embodiment of the present invention, anelectrosurgical device is contemplated. The device includes a probeextending in a longitudinal direction, wherein the probe includes aproximal region and a distal region, wherein an inner diameter of theprobe defines a lumen, wherein the probe has an electrically insulatedportion extending from the proximal region to the distal region and anelectrically exposed conductive portion located at the distal region,wherein the electrically exposed conductive portion deliversradiofrequency energy to an area of tissue adjacent the distal region ofthe probe; and a heat transfer system for removing thermal energy fromthe area of tissue, wherein the heat transfer system is in thermalcontact with the area of tissue, wherein the heat transfer systemremoves from about 0.1 Watts to about 50 Watts of energy from the areaof tissue.

In one particular embodiment, the heat transfer system can remove fromabout 2 Watts to about 12 Watts of energy from the area of tissue.

In another embodiment, the heat transfer system is at least partiallydisposed within the lumen.

In yet another embodiment, the heat transfer system can be configured toabsorb or remove thermal energy over a time period ranging from about 60seconds to about 300 seconds.

In still another embodiment, the heat transfer system can include a heatremoval material in thermal contact with the area of tissue. The heatremoval material can be disposed within the lumen, and/or can bepositioned on an exterior surface of the probe, an introducer, or acombination thereof.

Further, the heat removal material can include a heat transfer material,a heat sink, or a combination thereof.

In one particular embodiment, the heat transfer material can include athermally conductive material, one or more Peltier circuits, or acombination thereof. The thermally conductive material can include ametal, a ceramic material, a conductive polymer, or a combinationthereof.

When the thermally conductive material is a metal, the metal can includea silver paste.

Meanwhile, when the heat transfer material includes one or more Peltiercircuits, the one or more Peltier circuits can be positioned within ahub of the electrosurgical device, a handle of the electrosurgicaldevice, the distal region of the probe, the proximal region of theprobe, or a combination thereof, wherein a connection exists between theone or more Peltier circuits and the distal region of the probe.Further, each Peltier circuit can include a hot side and a cold side,wherein the hot side faces the proximal region of the probe and the coldside faces the distal region of the probe.

In yet another embodiment, when the heat removal material includes aheat sink, the heat sink can include a phase change material. The phasechange material can change phase at a temperature between about 40° C.and 100° C. In addition, the phase change material can have a heat offusion ranging from about 150 Joules/gram to about 300 Joules/gram.Moreover, from about 1 gram to about 12 grams of the phase changematerial can be required to remove from about 2 Watts to about 12 Wattsof energy from the probe over a 150 second time period. Further, thephase change material can include a paraffin wax. In one embodiment, thephase change material can surround a conductor extending from theelectrically exposed conductive portion of the probe at the distalregion of the probe towards a proximal end of the probe.

In still another embodiment, the heat sink can be a gas or a pressurizedliquid, wherein the gas or the pressurized liquid is contained withinthe lumen. Further, the gas can be carbon dioxide or nitrogen and theliquid can be liquid carbon dioxide. The lumen can contain an inletchannel, wherein the gas or pressurized liquid is introduced into thelumen, and an outlet channel where the gas or pressurized liquid exitsthe lumen, wherein the inlet channel and the outlet channel are definedby a separator, wherein the inlet channel has a diameter that is smallerthan a diameter of the outlet channel.

In yet another embodiment, the heat sink can include an endothermicreaction system, wherein the endothermic reaction system includes afirst material separated from a second material, wherein an endothermicreaction occurs when the first material contacts the second material.The first material can include water and the second material can includeammonium nitrate. Further, the first material and the second materialcan be stored in a cartridge that can be inserted into the lumen priorto use of the electrosurgical device. Moreover, such a heat transfersystem can further include a wire, where the wire facilitates thetransfer of heat from the electrically exposed conductive portion of theprobe to the endothermic reaction between the first material and thesecond material.

In yet another embodiment, wherein the heat transfer material can be inthermal communication with the heat sink.

In still another embodiment, the heat sink can be an external heat sink.Further, the heat transfer material can be in communication with theheat sink via one or more conductive wires or conduits.

In one more embodiment, the heat sink can include a series of fins,etchings, particulates, or a combination thereof so that the heat sinkexhibits increased surface area to facilitate removal of heat from thetissue.

In one more embodiment, the area of tissue adjacent the distal region ofthe probe can be maintained at a temperature of less than about 90° C.

In yet another embodiment, the heat transfer system can be free of acirculating liquid.

In still another embodiment, the heat transfer system can be free of apump.

Other features and aspects of the present disclosure are discussed ingreater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and aspects of the present disclosureand the manner of attaining them will become more apparent, and thedisclosure itself will be better understood by reference to thefollowing description, appended claims and accompanying drawings, where:

FIG. 1A is a perspective view of an embodiment of a probe that can beused in conjunction with one embodiment of the system contemplated bythe present invention;

FIG. 1B is a top view of the embodiment of FIG. 1A;

FIGS. 2A to 2D are perspective views showing configurations ofelectrically insulated portions and electrically exposed conductiveportions (i.e., active electrode portions) of several embodiments of aprobe that can be used in conjunction with the system contemplated bythe present invention;

FIGS. 3A to 3F are cross sectional views of several embodiments ofprobes with internal cooling that can be used in the system contemplatedby the present invention;

FIGS. 4A to 4C are partial perspective views showing configurations oftemperature measuring devices that can be used in several embodiments ofthe present invention;

FIGS. 5A to 5D are partial perspective views showing embodiments of adistal region of a probe that can be used in the system contemplated bythe present invention and examples of lesions formed therefrom;

FIG. 6 is a perspective view of an embodiment of a system contemplatedby the present invention;

FIG. 7 is a comparative partial perspective view showing the distalregion of an embodiment of a probe that can be used in the system of thepresent invention and examples of lesions that may be formed withvarious degrees of cooling;

FIG. 8A is a graph of temperature in a uniform tissue vs. relativedistance using an embodiment of a probe that can be used in the systemof the present invention with cooling and without cooling;

FIG. 8B is a graph of energy in a uniform tissue vs. relative distanceusing an embodiment of a probe that can be used in the system of thepresent invention with cooling and without cooling;

FIG. 9 is a top view of an embodiment of a probe of the presentinvention positioned within an intervertebral disc of a patient;

FIG. 10 is a view of the cervical vertebrae of a patient's spine,showing target sites for facet denervation;

FIGS. 11A and 11B illustrate various positions of a probe that can beused in the system of the present invention with respect to the C3-C5region of the cervical vertebrae;

FIG. 12 illustrates a probe that can be used in the system of thepresent invention, where the probe is positioned at the lumbar region ofthe spine;

FIG. 13 is a view of the thoracic vertebrae of a patient's spine,showing a target site for energy delivery;

FIG. 14 illustrates a position of a probe that can be used in the systemof the present invention with respect to the thoracic vertebrae;

FIG. 15 shows a plan view of the sacroiliac region of a human;

FIGS. 16A-16C show a lesion as would be formed by a probe of the priorart;

FIG. 17 illustrates a cross-sectional view of a system contemplated bythe present invention that includes a probe and an introducer with aside port for liquid delivery to a lesion site;

FIG. 18 illustrates a cross-sectional view of a system contemplated bythe present invention that includes a probe and an introducer with aside port for venting during treatment (e.g., lesioning);

FIG. 19 illustrates a cross-sectional view at point 2C of FIG. 17showing the lumen created between the outer diameter of the probe andthe inner diameter of the introducer;

FIG. 20 illustrates a cross-sectional view of a system contemplated bythe present invention that includes a probe and an introducer with aT-joint having a side port positioned there between for liquid deliveryto a lesion site; and

FIG. 21 illustrates a cross-sectional view of a system contemplated bythe present invention that includes a probe and an introducer with aT-joint having a side port positioned there between for venting duringtreatment (e.g., lesioning).

Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the present disclosure. The drawings are representationaland are not necessarily drawn to scale. Certain proportions thereofmight be exaggerated, while others might be minimized.

DETAILED DESCRIPTION

Reference will now be made in detail to one or more embodiments of theinvention, examples of the invention, examples of which are illustratedin the drawings. Each example and embodiment is provided by way ofexplanation of the invention, and is not meant as a limitation of theinvention. For example, features illustrated or described as part of oneembodiment may be used with another embodiment to yield still a furtherembodiment. It is intended that the invention include these and othermodifications and variations as coming within the scope and spirit ofthe invention.

Generally, the present invention is directed to an electrosurgicaldevice that includes a probe extending in a longitudinal direction,wherein the probe includes a proximal region and a distal region, andwherein an inner diameter of the probe defines a lumen. The probe has anelectrically insulated portion extending from the proximal region to thedistal region and an electrically exposed conductive portion located atthe distal region, wherein the electrically exposed conductive portiondelivers radiofrequency energy to an area of tissue. The electrosurgicaldevice also includes a cooling or heat transfer system that is inthermal contact with the area of tissue, where the cooling or heattransfer system is capable of removing from about 0.1 Watts to about 50Watts, such as from about 0.5 Watts to about 40 Watts, such as fromabout 1 Watt to about 25 Watts, such as from about 2 Watts to about 12Watts from the area of tissue through the electrosurgical device inorder to prevent charring or carbonization of the tissue. In addition,the cooling or heat transfer system can be designed in such a mannerthat it does not require the use of a peristaltic pump to circulate aliquid (e.g., water) inside a lumen of the probe in order tosufficiently cool the area of tissue being treated. In one particularembodiment, the cooling or heat transfer system can be at leastpartially disposed within a lumen of the probe, while in otherembodiments, the cooling or heat transfer system can be positioned on anexterior surface of the probe, an introducer component of theelectrosurgical device, or a combination thereof so long as the coolingor heat transfer system is in thermal communication with the area oftissue being treated, such as via a thermally conductive region of theprobe located at the distal end or distal region of the probe.

For instance, the heat transfer system can include a heat removalmaterial that can include a heat transfer material, a heat sink, or acombination thereof. The heat removal material can be placed in thermalcontact with the area of tissue being treated and can be used totransfer heat away or absorb heat from an interface between the tissueand the probe of the electrosurgical device. Further, when the heatremoval material includes both a heat transfer material and a heat sink,the heat transfer material can direct the heat towards the heat sink,which then absorbs the heat from the tissue. As discussed below, varioustypes of materials can be used for the heat transfer material and theheat sink. Regardless of the specific material used for the heattransfer material specifically, the heat transfer material can have aheat transfer coefficient that is sufficiently high enough to maintainthe tissue temperature at the tissue/probe interface below a desiredtemperature, such as below about 90° C., which is the temperature atwhich charring and carbonization of the tissue can occur and thetemperature at which tissue impedance spikes. Specific embodimentscontemplated by the present invention are discussed in detail below.

Referring now to the drawings, and beginning with FIGS. 1A and 1B,various features of the device are discussed in more detail. As shown,the electrosurgical instrument or device may be a probe 100; however, inother embodiments, the electrosurgical instrument or device may be acannula, a catheter, or any other elongate member capable of deliveringenergy to a target site within a patient's body. For the sake ofclarity, the term “probe” is used throughout the specification todescribe any such device. The probe 100 may be an elongate member thatcan include a shaft 122, a distal region 104, a distal end 106, a distalface 107, a proximal region 108, and a proximal end 110. As used herein,the terms “distal” and “proximal” are defined with respect to the userand when the device is in use. That is, the term “distal” refers to thepart or portion further away from the user and closest to the treatmentsite, while the term “proximal” refers to the part or portion closer tothe user and farthest from the treatment site when the device is in use.

As shown in the embodiments contemplated by FIGS. 1A and 1B, the probe100 can include an electrically insulated portion 116 and anelectrically exposed conductive portion 118. The electrically exposedconductive portion 118 can also be referred to as an active electrode,and when the exposed conductive portion is located at the distal end ofprobe 100, it may be referred to as an active tip. In general, theelectrically insulated portion 116 may extend from the proximal region108 of the probe 100 to a location in the distal region 104 of the probe100. The location to which electrically insulated portion 116 extendsmay depend on the application, as will be discussed in more detailbelow. Furthermore, the location to which electrically insulated portion116 extends may not be fixed. In other embodiments, as shown in FIGS. 2Ato 2D, the probe 100 can include more than one electrically insulatedportion 116 and/or more than one electrically exposed conductive portion118.

In some embodiments, for example as shown in FIG. 1A and 1B, theproximal region 108 of the probe 100 can include a hub 114. The hub 114may be structured to securely connect other devices such as introducers,connector cables, cannulae, tubes, or other hubs, for example, to theprobe 100. For example, as shown in FIG. 6 and discussed in furtherdetail below, the probe 100 may be coupled to an energy source and/or toa source of cooling via respective connecting means (for example, anelectrical cable and/or flexible tubing) which may be associated withthe hub 114 (also shown in FIG. 3). The hub 114 may also serve as ahandle or grip for the probe 100 and can serve as a locking mechanism tosecure the probe 100 to an introducer 604, as discussed in more detailbelow with respect to FIGS. 17 to 21. The hub 114 may be manufacturedfrom a number of different materials, including, but not limited to,plastics, polymers, metals, or combinations thereof. Furthermore, thehub 114 may be attached to probe 100 by a number of different means. Forexample, in one embodiment, the hub 114 may be made from polypropylene,and may be attached to probe 100 by any suitable fitting such as a luerfitting. Although the hub 114 can serve as a handle, it is also to beunderstood that a separate handle 120 is also contemplated (see FIG. 6).

The size and shape of the probe 100 may vary depending on theapplication, and the invention is not limited in this regard. Forexample, in some embodiments, the transverse cross sectional shape ofthe probe 100 may be substantially circular. In other embodiments, thecross-sectional shape may be substantially polygonal, elliptical, or anyother desired shape. In some embodiments, the length from the distal end106 to proximal end 110 of the probe 100 may be between about 5centimeters (cm) and about 40 cm and the outer diameter of shaft 122 maybe between about 0.65 millimeters (mm) and about 2.00 mm (between about20 AWG and about 12 AWG). In one specific example, the length of theprobe may be about 7.5 cm, the outer diameter may be about 1.5 mm, andthe transverse cross-sectional shape may be substantially circular.Further, it is to be understood that the shape of the distal end 106 mayvary depending on the application. Possible shapes include, but are notlimited to, blunt, rounded, sharp, and beveled.

The probe 100 may be rigid or flexible and may be straight, bent orangled at one or more points along its length. As used herein, the term“bent” refers to any region of non-linearity or any deviation from alongitudinal axis, gradual or abrupt, and at any angle. In embodimentswherein the probe 100 is bent, the bend may be at various locationsalong the probe 100, for example in the distal region 104. Furthermore,the bend may be of a variety of degrees and lengths. For example, thebend may traverse about 25° of a circle, and occur over a length ofabout 5 mm. In addition, the probe 100 can include a plurality of bends,which may or may not be in the same plane. For example, in someembodiments, the probe 100 may be bent such that it is helical or“corkscrew” shaped. In some embodiments, the probe 100 may be structuredsuch that its shape may be modified by a user before or during thecourse of a procedure. More specifically, the shape of the distal region104, for example, may be modified such that it may change from astraight to a bent configuration using an actuating mechanism. This mayaid in accessing difficult to reach sites within the body and can beaccomplished by a variety of means. For example, the probe 100 caninclude at least one active shape control mechanism, including but notlimited to one or more pull-wires, a hydraulic or piezoelectric device,or another actuating mechanism.

In one embodiment, the electrically insulated portion 116 may be formedby coating a portion of the shaft 122 with an electrically insulativecoating, covering, or sheathing. In other words, the probe 100 caninclude electrically insulative material disposed on the surface of theelongate member. For example, in one embodiment, the shaft 122 of theprobe 100 may be fabricated from a biocompatible metal or alloy, forexample stainless steel, which may be overlaid in part by an insulatingcoating, for example polytetrafluoroethylene (PTFE). In otherembodiments, the shaft 122 can be fabricated from another metal, such asnitinol or titanium, and/or another electrically insulating material,including but not limited to polyethylene terephthalate (PET), may bedisposed thereon. In other embodiments, other metals or electricallyinsulating materials may be used, and the invention is not limited inthis regard. Furthermore, the insulating material may be semi-porous, toallow for some leakage of current through the insulating material. Insome embodiments, the material may also be a thermal insulator as well.In still other embodiments, different insulating materials can be usedfor different portions of the probe 100. The insulating coating may beapplied to a portion of shaft 122 by dip-coating, spraying or heatshrinking, for example. Meanwhile, the remaining uncoated portion of thedistal region of the shaft 122 may serve as a conductive portion 118.

In another embodiment, the shaft 122 of the probe 100 can be fabricatedfrom an insulative or non-conductive material and may be furnished withone or more externally applied electrodes 118. In such embodiments, theprobe 100 can include one or more wires that may be attached to theelectrode(s) 118 at one end, and can run proximally along the shaft 122,such that a proximal portion of the wire(s) may be operatively connectedto an energy source, thereby supplying energy to the electrodes 118. Forexample, the shaft 122 can be fabricated from Radel™ plastic, and theexternally applied electrodes can be fabricated from stainless steel.

In alternate embodiments, the shaft 122 may be manufactured from acombination of materials. For example, the distal region 104 of theshaft 122 can be made from a material such as nitinol, such that theshape of the distal region 104 may be altered, and the remainder ofshaft 122 may be made from stainless steel, such that the remainder ofshaft 122 may be substantially fixed.

As discussed above, the electrosurgical device of the present inventioncontemplates a probe 100 that can include a heat transfer system tofacilitate cooling of the area tissue being treated via various heattransfer materials, heat sinks, or a combination thereof. Severalembodiments of the internal structure of the probe 100 of FIG. 1incorporating various cooling or heat transfer systems contemplated bythe present invention are shown FIGS. 3A to 3F, which representcross-sectional view of the probe 100 of FIG. 1B at cut line 1C.

Turning first to FIG. 3A, an electrosurgical device including a probe100A with one embodiment of a cooling or heat transfer systemcontemplated by the present invention is shown. In order to facilitatesufficient cooling of the tissue being treated during use of theelectrosurgical device, the lumen 124 of the probe 100A can be filledwith a heat transfer material such as a thermally conductive ceramicmaterial 153 or any other suitable heat transfer material. Any suitableceramic material can be used as long as it has a sufficiently highthermal conductivity to facilitate transfer of the heat from the tissueto the ceramic material 153. Examples include but are not limited toalumina, aluminum nitride, beryllium oxide, boron nitride or acombination thereof. Regardless of the particular ceramic materialutilized, the ceramic material can have a thermal conductivity(sometimes called “Lambda”) of at least about 20 W/mK (Watts per kelvinper meter), such as a thermal conductivity ranging from about 20 W/mK toabout 400 W/m K, such as from about 25 W/mK to about 375 W/m K, such asfrom about 30 W/mK to about 350 W/m K.

Regardless of the particular type of ceramic material used for thethermally conductive ceramic material 153, the thermally conductiveceramic material 153 can be positioned inside the lumen 124 of the probe100A. However, it is to be understood that the thermally conductiveceramic material 153 can be located on any suitable surface or withinany component of the electrosurgical device so long as it is incommunication with a thermally conductive region of the probe 100A inorder to facilitate cooling of the tissue near the thermally conductiveregion of the probe 100A. For instance, it is also possible to wrap theexterior surface of the probe 100A with the thermally conductive ceramicmaterial 153 in order to facilitate the transfer of the heat away fromthe tissue. In addition, other components of the electrosurgical device,such as the introducer 604 (see FIG. 6), can also be formed from thethermally conductive ceramic material 153 or can be in contact with thethermally conductive ceramic material 153 to facilitate heat transferaway from the tissue.

Further, the present invention also contemplates the use of any otherthermally conductive material 134 (e.g., a metal, a conductive polymer,or a combination thereof) to cool a probe 100B, as shown in FIG. 3B,where the thermally conductive material 134 can be used to transfer heataway from a region of tissue and the distal face 107 of the probe 100B.Although FIG. 3B is discussed below with respect to a metal (e.g.,silver paste), conductive polymers can also be used alone or incombination with a metal or any other thermally conductive material,such as the thermally conductive ceramic materials discussed above. Theconductive polymer can be a pre-compounded polymer resin or can be acombination of a base polymer resin and one or more thermally conductiveadditives (e.g., boron nitride, carbon fibers, carbon powder, stainlesssteel fibers, nickel-coated graphite, etc. or a combination thereof).

Specifically, the lumen 124 of the probe 100B can be filled with thethermally conductive material 134. By filling the probe 100B with thethermally conductive material 134, heat can easily flow away from theactive tip at the distal face 107 of the probe 100B and could betransferred to a heat sink, such as heat sink 136, which can be madefrom any of the heat sink materials discussed in the present applicationin more detail below. In one particular embodiment, the thermallyconductive material 134 can include a metal, such as a silver paste, andthermally conductive wires 132 can be positioned in the paste, where thethermally conductive wires can exit the proximal end 110 of the probe1006 and lead to the heat sink 136. Such an arrangement can provide foran external cooling source that is not confined by the space of theprobe 1006 to allow for additional cooling, although it is to beunderstood that the heat sink 136 can alternatively be located withinthe probe or other components of the electrosurgical device (hub,handle, introducer/cannula, etc.). In addition, it is to be understoodthat the thermally conductive material 134 can be located on anysuitable surface or within any component of the electrosurgical deviceso long as it is in communication with a thermally conductive region ofthe probe 1006 in order to facilitate cooling of the probe. Forinstance, the thermally conductive material 134 can be positioned on anexterior surface of the probe 1006, an introducer (see introducer 604 inFIG. 6), or a combination thereof. Moreover, it is to be understood thatalthough the heat sink 136 is shown as being external, it can be locatedwithin the probe 100B or any of the other components of theelectrosurgical device as well. Further, although the heat sink 136 isshown in use with a thermally conductive metal as the heat transfermaterial, the heat sink 136 can be used in conjunction with any of theheat transfer materials discussed with respect to FIGS. 3A-3C.

The heat sink 136 can be any material with a high specific heat, a phasechange material, materials to initiate an endothermic chemical reaction,pressurized liquids, gases, or any other suitable material. In otherwords, the heat sink 136 can be formed from any material that can absorbheat away from the distal end 106 and/or distal region 104 of the probe1006 and can that has a high heat capacity where the energy beingtransferred from the tissue through the heat transfer material (e.g.,thermally conductive ceramic material, metal, thermally conductivepolymer, etc.) to the heat sink 136 acts to slowly increase thetemperature of the heat sink 136 such that the during the course of theradiofrequency treatment, the interface between the probe and the tissueis maintained at a temperature of less than about 90° C. Moreover, itshould be understood that if a liquid is used in the heat sink 136, theliquid does not need to be circulated in and out of the heat sink 136and can be stagnant and fully contained within the heat sink 136. Inaddition, the heat sink 136 can possess a high surface area where theenergy being transferred from the tissue through the heat transfermaterial to the heat sink 136 is dissipated through convective orradiative cooling to the environment such that during the course of theradiofrequency treatment, the interface between the probe and the tissueis maintained at a temperature of less than about 90° C., where the highsurface area can be created through a series of fins, etchings,particulate deposition steps, etc.

Referring now to FIG. 3C, the present invention also contemplates aprobe 100C where the tissue being treated can be cooled by athermoelectric circuit that includes one or more Peltier circuits, whichcan be arranged in series or in any other suitable arrangement.Specifically, the probe 100C may partially or fully house a circuitcomprising two dissimilar metals or semiconductors, for example P- andN-doped bismuth-telluride, which are joined together at two junctions.When current passes through the circuit, heat may be transferred fromone junction to the other.

This phenomenon is known as the Peltier effect. The junction where theheat is transferred from may be located in the distal end 106 of theprobe 100C, and the junction where the heat is transferred to may belocated at a proximal end 110 of the probe 100C or externally to theprobe 100C. Energy may be provided to the circuit by an external energysource (for example, the same energy source that delivers RF energy tothe probe 100C), or an additional power source 137 such as an electricalgenerator or a battery, for example.

In one particular embodiment, at least two Peltier circuits 138A and138B are positioned within the lumen 124 of the probe 100C. The Peltiercircuit 138A includes a hot side 139A and a cold side 140A, while thePeltier circuit 138B includes a hot side 139B and a cold side 140B,where the hot sides 139A and 139B are heated up and may be in thermalcontact with any of the heat sinks discussed herein in order tofacilitate cooling of the cold sides 140A and 140B, which are positionedcloser to the distal end 106 of the probe 100C to cool the distal face107 and tissue adjacent thereto. In other embodiments, additionalPeltier circuits 138C, 138D, 138E, and 138F can also be utilized toprovide additional cooling, where the circuits include hot sides 139C,139D, 139E, and 139F positioned closer towards the proximal end 110 ofthe probe 100C and cold sides 140C, 140D, 140E, and 140F positionedcloser towards the distal end 106 of the probe 100C. By utilizing aseries of Peltier circuits as discussed above, such as at the individualPeltier circuits can use less energy and have smaller temperaturedifferences, which translates to the handle 120 not heating up so muchthat it could not be grasped by a user. Further, although the Peltiercircuits 138A through 138F are shown as being positioned within thelumen 124 of the probe 100C from its proximal region 108 or proximal end110 to its distal region 104 or distal end 106, the Peltier circuit orcircuits can alternatively or additionally positioned within the hub 114of the electrosurgical device, a handle of the device, etc. as long as aconnection exists between the one or more Peltier circuits and thedistal end 106 of the probe 100C.

Referring now to FIG. 3D, an electrosurgical device including a probe100D with another embodiment of a cooling or heat transfer systemcontemplated by the present invention is shown. In order to facilitatesufficient cooling of the tissue being treated during use of theelectrosurgical device, the lumen 124 of the probe 100D can be filledwith a phase change material 154, which acts as a heat sink. Cooling ofthe tissue via a phase change material 154 utilizes a method by which aphase change material is brought up to a temperature when it begins tochange phase from either a liquid to a gas or a solid to a liquid. Oncethe phase change process begins, the temperature of the phase changematerial 154 will not increase, but the phase change material 154 willcontinue to absorb heat from the surrounding environment until theentire phase change material 154 has changed phase.

In one particular embodiment, the phase change material 154 can be a wax(e.g., paraffin wax or any other suitable wax) that changes phase at atemperature between about 40° C. and about 100° C., such as atemperature between about 45° C. and about 95° C., such as at atemperature of between about 50° C. and about 90° C. For example, for aphase change material 154 that is a wax having a phase changetemperature of 50° C., its temperature will stay at 50° C., but the waxwill continue to absorb heat from the probe 100D and tissue at a ratedependent upon the heat of fusion of the particular wax or other phasechange material 154 utilized until all such wax has transitioned fromthe sold state to the liquid state. In one particular embodiment whenthe phase change material 154 is a paraffin wax, which has a heat offusion of about 200 J/g, in order to sink 6 Watts of energy from thetissue and probe 100D over a 150 second period, which equals about 900Joules, about 4.5 grams of the paraffin wax would need to change phase.Thus, depending on the particular phase change material utilized, fromabout 1 gram to about 12 grams, such as from about 3 grams to about 6grams, such as from about 3.5 grams to about 5 grams, such as from about4 grams to about 4.5 grams of the phase change material needs to changephase to sufficiently cool the tissue (e.g., remove from about 2 Wattsof energy to about 12 Watts of energy from the tissue and probe) whenthe phase change material has a heat of fusion ranging from about 150J/g to about 300 J/g, such as from about 175 J/g to about 275 J/g, suchas from about 200 J/g to about 250 J/g.

In any event, the phase change material 154 can be filled in the lumen124 of the probe 100D so that the phase change material 154 is incontact with the electrically exposed conductive portion 118 of theprobe 100D so that there is sufficient thermal contact with the area oftissue being treated. Further, the phase change material 154 cansurround a conductor 156 that extends from the electrically exposedconductive portion 118 at the distal face 107 of the probe 100D to theproximal region 108 of the probe 100D, where the conductor runs throughthe center of the phase change material 154 to provide improved heattransfer away from the distal face 107 of the probe 100D. In addition,it is to be understood that the phase change material 153 can be locatedon any suitable surface or within any component of the electrosurgicaldevice so long as it is in communication with a thermally conductiveregion of the probe in order to facilitate cooling of the probe. Forinstance, the phase change material 154 can be positioned on an exteriorsurface of the probe 100D, an introducer (see introducer 604 in FIG. 6),or a combination thereof.

Next, referring to FIG. 3E, an electrosurgical device including a probe100E with another embodiment of a cooling or heat transfer systemcontemplated by the present invention is shown. In order to facilitatesufficient cooling of the tissue being treated during use of theelectrosurgical device, the lumen 124 of the probe 100E can be filledwith gas such as nitrogen or carbon dioxide or a pressurized liquid suchas liquid carbon dioxide to as act as a heat sink. As shown in FIG. 3E,the gas or pressurized liquid 160 can be delivered to the lumen 124 ofthe probe 100E from a gas or pressurized liquid source 145 via an inlet142 and into an inlet channel 143 inside the lumen 124. Then, the gas orpressurized liquid 160 can travel through the inlet channel 143 from theproximal region 108 of the probe 100E to the distal end 106 of the probe100E, where the gas or pressurized liquid then enters an outlet channel144 and travels from the distal end 106 of the probe 100E to theproximal region 108 of the probe 100E, where the gas or pressurizedliquid 160 can exit the probe 100E via outlet tubing 147. Referring toFIG. 3E, a separator 146 can be used to form the inlet channel 143 andthe outlet channel 144.

The gas or pressurized liquid 160 can be introduced to the probe 100Esuch that the gas or pressurized liquid 160 expands near the distal face107 of the probe 100E. As the gas or pressurized liquid 160 expands, thetemperature of the tissue and probe 100E at the distal face 107 can belowered to provide cooling to the tissue and probe 100E according to theideal gas law PV=nRT, where P=Pressure, V=Volume, n=number of moles,R=Universal gas constant, and T=Temperature, where it follows that ifthe pressure drops due to expansion, the temperature will also drop. Inone particular embodiment, the gas or pressurized liquid expands at thedistal face 107 due to an increase in diameter D2 of the outlet channel144 and optional outlet tube 147 as compared to the diameter D1 of theinlet tube 142 and inlet channel 143, which, in turn, results in adecrease in temperature of the gas or pressurized liquid, which, inturn, results in a decrease in temperature at the distal face 107 of theprobe 100E. It is to be understood that as the pressurized liquidexpands, it changes phase into a gas so that the pressurized liquidleaves the outlet channel 144 as a gas. It is also to be understood thatthe probe 100C is designed to withstand the increased pressures at theinlet channel 143 as well as the cooling that occurs.

In an alternate embodiment, as shown in FIG. 3F, the present inventioncontemplates a probe 100F where the tissue being treated may be cooledchemically, such as via an endothermic reaction between two materials,where the reaction between the two materials acts as a heat sink toabsorb heat from the tissue. For instance, the two materials can bewater and ammonium nitrate. The materials can be stored separately suchthat when mixed, an endothermic reaction or endothermic mixing occurs.When the materials mix, thermal energy will be absorbed, and the distalregion 104 of the probe 100F near the distal face 107 will be cooled,which then facilitates cooling of the tissue being treated with theelectrosurgical device. Cooling can be facilitated via a wire 153, whichcan be made of copper, where the wire 153 can transfer the heat from theactive tip at the distal face 107 to the reaction. The product(s) of theendothermic reaction or the resulting mixture may exit the probe 100Fvia the open proximal end 110.

One example of a suitable reaction for the chemical cooling of thetissue being treated via the probe 100F may be the mixing of water andammonium nitrate, where the water is contained in water channel 148 thatis closed at the distal end 106 of the probe 100F via a seal 158 thatcan be ruptured via any suitable means, such as by pressing a button 162or by twisting, to cause the water, which can be stored in water source150, to mix with the ammonium nitrate, which can be stored in anadditional channel 149. In one particular embodiment, in order to sinkfrom about 2 Watts of energy to about 12 Watts of energy from the tissueand probe 100F over up to a 150 second period, from about 0.2 grams toabout 5 grams of water, such as from about 0.3 grams to about 4 grams ofwater, such as from about 0.4 grams of water to about 3 grams of watercan be mixed with from about 0.5 grams to about 7 grams of ammoniumnitrate, such as from about 0.6 grams to about 6 grams of ammoniumnitrate, such as from about 0.7 grams to about 5 grams of ammoniumnitrate. In one particular embodiment, 1.4 grams of water and 2.1 gramsof ammonium nitrate can be used to remove about 6 Watts of energy fromthe tissue and probe 100F. The water and ammonium nitrate can be storedin a cartridge that can be inserted into the lumen 124 of the probe 100Fjust prior to use, or the water can be introduced into water channel 148via tubing, such as tubing 151 that can deliver water from water source150 into water channel 148, while the ammonium nitrate can be stored inits channel 149, which can surround the water channel 148 as shown inFIG. 3F. In addition, it is to be understood that the two materials(e.g., water and ammonium nitrate) can be located on any suitablesurface or within any component of the electrosurgical device so long asthe two materials, upon mixing, are in communication with a thermallyconductive region of the probe in order to facilitate cooling of theprobe 100F. For example, the two materials (e.g., water and ammoniumnitrate) can be positioned on an exterior surface of the probe 100F, anintroducer (see introducer 604 in FIG. 6), or a combination thereof.

Regardless of the particular combination of heat transfer materials andheat sink materials utilized, according to an aspect of the invention,it is desirable to absorb or remove thermal energy from the distalregion of the probe over a period of time that corresponds to the lengthof an electrosurgical procedure in order to transfer heat away from aregion of tissue. Generally speaking, it is desirable to absorb orremove from about 0.1 Watts to about 50 Watts of energy from the distalregion of the probe to transfer heat away from area of tissue over atime period that may range from about 60 seconds to about 300 seconds.For example, it is desirable to absorb or remove from about 1 Watt toabout 25 Watts of energy from the distal region of the probe to transferheat away from area of tissue over a time period that may range fromabout 90 seconds to about 240 seconds. As another example, it isdesirable to absorb or remove from about 2 Watt to about 15 Watts ofenergy from the distal region of the probe to transfer heat away fromarea of tissue over a time period that may range from about 100 secondsto about 200 seconds. As yet another example, it is desirable to absorbor remove from about 2 Watt to about 12 Watts of energy from the distalregion of the probe to transfer heat away from area of tissue over atime period that may range from about 125 seconds to about 175 seconds.In one particular embodiment, the heat transfer system can remove fromabout 2 Watts to about 12 Watts of energy over about 150 seconds.

In some embodiments, any of the probes 100A-F discussed above can besterilizable. The probe 100 can be sterilized by, for example, steam,ethylene oxide, or radiation sterilization without risk of materialdegradation or discoloration. In order for the probe 100 to besterilizable, the probe 100 can be made from sterilizable materials. Forinstance, the shaft 122 can be made from stainless steel and theelectrically insulative coating 116 may be made from PTFE.

In some embodiments, the probe 100 can include at least one temperaturesensing device 112 (i.e., a temperature sensor), as shown in FIGS.1A-1B, 3A-3F, 4A-4C, and 6. The temperature sensing device 112 can beany means for sensing and/or measuring temperature, including, but notlimited to, a thermocouple, a thermistor, an optical fluorescencesensor, or a resistance thermometer. In some embodiments, thetemperature sensing device 112 can be positioned at the distal region104 of the probe 100, for example at distal end 106. As shown in theembodiments of FIGS. 4A to 4C, the temperature sensing device 112 canhave various configurations. For example, as shown in FIG. 4A, thetemperature sensing device 112 can be disposed at the distal end 106 andcan be substantially flush with the distal end 106. In anotherembodiment, as shown in FIG. 4B, the temperature sensing device 112 canprotrude from the distal end 106, such that it may measure thetemperature of a material that is located distal to distal end 106,rather than the temperature of the probe 100 itself or of materialadjacent to the probe 100. In another embodiment, as shown in FIG. 4C,the temperature sensing device 112 can be located proximally to thedistal end 106. In further embodiments, the probe 100 can includeadditional temperature sensing devices. For example, a first temperaturesensing device may be located at the distal end 106 of the probe 100,and a second temperature sensing device may be located distal to thedistal end 106 of the probe 100, such that the temperature at the distalend 106 of the probe 100 as well as in the tissue may be measured. Inother embodiments, other configurations are possible, and the inventionis not limited in this regard. Furthermore, in the embodiments shown inFIGS. 4A and 4C, the temperature sensing device may be located withinthe probe 100, or on the external surface of the probe 100.

In an alternate embodiment, the temperature sensing device 112 can belocated within the lumen 124 of the probe 100 so as to measure thetemperature of one or more components of a cooling/heat transfer systemcontained therein. By monitoring the change in temperature of thecooling fluid, which relates to the amount of heat being drawn away fromthe probe 100, the temperature of the tissue located adjacent conductiveportion 118 can be determined.

In some embodiments, the probe 100 can include means for operativelyconnecting the temperature sensing device 112 to an external device. Forexample, such a device can be a display or screen, such that thetemperature measured by the temperature sensing device may be viewed bya user. In other embodiments, the external device can be an electricalgenerator, such that temperature feedback can be provided to theelectrical generator. Means for operatively connecting the temperaturesensing device 112 to an external device can include an insulated wire128, which can extend proximally from the temperature sensing device112, through the lumen 124 of the probe 100, and out of the probe 100through its proximal end 110. The wire 128 can be any temperature orelectrical conductor capable of operatively connecting the temperaturesensing device 112 to an external device. Alternatively, the temperaturesensing device 112 can be operatively connected to an external devicevia a wireless connecting means, including, for example, infrared orBluetooth™. Further details regarding temperature sensing devices can befound in U.S. Patent Application Publication No. 2005/0177209 to Leung,et al., which is incorporated herein by reference.

In some embodiments, the probe 100 can include a sensor for measuringimpedance. As the impedance of a tissue may be a characterizing factor,measuring the impedance of tissue proximal to the probe 100 can helpconfirm placement within a desired tissue type. In some embodiments, theprobe 100 can be structured to measure the electrical impedance between,for example, two points on the probe 100 or between a point on theconductive portion 118 and a point on an auxiliary device such as acannula or a grounding pad. Further details regarding impedancemeasuring means may be found in U.S. Patent Application Publication2005/0177209 to Leung, et al., which is incorporated herein byreference.

In some embodiments, the probe 100 can include a sensor for measuringpressure. The means of measuring pressure can include a lumen in fluidcommunication with fluid in a patient's body as well as with a pressuretransducer to record the pressure measurements. In other embodiments,the pressure sensor can include a pressure transducer disposed at adesired location on the probe 100.

As mentioned above with respect to the temperature sensing device, theprobe 100 can include means for operatively connecting any impedance orpressure measuring means to an external device. For example, a pressuretransducer may be electrically coupled to a wire located within theprobe 100, which wire may be further electrically coupled to an externaldevice to transmit a signal from the pressure transducer to the externaldevice.

In some embodiments, probe 100 can include means for enhancing thevisualization thereof, for example when viewed under fluoroscopicimaging or another imaging modality. Such means may be a visible marker,a radiopaque marker or markers for use with magnetic resonance imagingor ultrasound, for example. Further details regarding enhancedvisualization are disclosed in U.S. Pat. No. 7,593,778 to Chandran, etal. and U.S. Patent Application Publication 2004/0176759 toKrishnamurthy, et al., both of which are incorporated herein byreference.

In some embodiments, the hub 114 can have markings to indicate, forexample, the direction/orientation of a bend or curve of the probe 100or the location of an aperture or a temperature or pressure sensingdevice on or within the probe 100. These markings may be visualindicators, or tactile indicators, which may be textured or raised sothat the user may see or feel the markings while manipulating the probe100.

In some embodiments, a proximal end of the probe 100 can include astrain relief, which can additionally include a grip running from theproximal end to the distal end of the strain relief. A strain relief canbe, for example, a soft flexible bend relief able to support any cableor tubing exiting the proximal end of the probe 100.

As mentioned hereinabove, the size and/or geometry of electricallyinsulating region 116 and the conductive portion 118 may differdepending on the specific application. As disclosed in U.S. PatentApplication Publication No. 2007/0156136 to Godara, et al. and U.S. Pat.No. 7,819,869 to Godara, et al., which are incorporated herein byreference, when sufficient energy is delivered from an energy sourcethrough an active electrode to a tissue of a patient's body, a lesionmay form in the tissue wherein the size, shape, and location of thelesion are at least partially dependent on the size and/or geometry ofthe active electrode.

Exemplary embodiments of probes 100 having a conductive portion 118 ofvarious geometries, and being of between about 16 AWG and about 19 AWG,and examples of lesions 502 that may be formed therefrom are illustratedin FIGS. 5A to 5D, by way of non-limiting example only. Referring firstto FIG. 5A, when conductive portion 118 of probe 100 is elongate, forexample having a length of between about 4 mm and about 6 mm asubstantially oblate lesion 502 may form around conductive portion 118.Due to edge effects, the distribution of energy may not be equal aroundall portions of the conductive portion 118, and a large portion of thecurrent may exit the conductive portion 118 in the region closest to theelectrically insulated portion 116. Thus, the widest portion of thelesion may form in the area adjacent the electrically insulated portion116. In use, such a conductive portion may be positioned such that itlies substantially parallel to the surface of the tissue to be lesioned(target site) in order to provide maximum efficacy.

Referring now to FIG. 5B, when the electrically conductive portion 118of the probe 100 is shortened and, for example, has a length of betweenabout 2 mm and about 4 mm, a substantially more rounded lesion 502 mayform around the conductive portion 118. Due to the shorter length of theconductive portion 118, the lesion 502 may extend distally further fromthe probe 100 than the lesion shown in FIG. 5A.

In some embodiments, the electrically insulated portion may extendsubstantially from the proximal region 108 of the probe 100 to thedistal end of probe 100. For example, the electrically insulated portion116 may terminate at the distal face of the probe such that the distalface 107 of the probe 100 includes at least one electrically exposedconductive portion 118. As will be apparent to the person skilled in theart, depending upon the geometry of the probe, the electricallyinsulated portion may terminate slightly proximal to the distal face solong as the energy delivery remains substantially distal. In someembodiments, a portion of the distal face 107 can include at least oneconductive portion 118 as shown, for example, in FIGS. 2B-2D. Referringnow to FIG. 5C, a probe 100 having a distal face 107 that includeselectrically exposed conductive portion 118 is shown. In suchembodiments, if distal face 107 is rounded (as shown in FIG. 5C), therounded face or surface can include the conductive portion 118; if thedistal face 107 is flat, the flat surface can include the conductiveportion 118, and so on. In these embodiments, a lesion 502 may formwherein the lesion forms substantially distal to the distal face 107,for example, such that the majority of the lesion 502 is located distalto the distal face 107 of the probe 100, and the shape of the lesion 502may be substantially rounded, for example the ratio of the length of thelesion 502 (i.e., the dimension along the longitudinal axis of the probe100) to the width of the lesion 502 (i.e., the dimension perpendicularto the longitudinal axis of the probe 100) may be about 1:1. In use,such a probe 100 may be positioned such that it is orientedsubstantially perpendicular or generally upstanding to the target siteor surface of the tissue to be lesioned (i.e., such that the tissue tobe lesioned is generally distal to the probe 100, whereby the lesion 502may extend distally from the probe 100 to the target tissue. This canprovide significant advantages in a region of the body such as thesacroiliac region (shown in FIG. 15) having a rough or uneven surface,because the conductive portion 118 can be positioned to lesion tissuedisposed in rifts and valleys between bony structures, or in fissures orgrooves in the surface of a bony structure, as is described in detailbelow. In further embodiments, the conductive portion 118 may be offsetfrom an axis of the probe 100 such that the electrically exposedconductive portion 118 is not symmetrical about the axis of the probe100, as shown for example in FIG. 5D.

In some embodiments, the probe 100 may be structured to have aconductive portion 118 of a fixed size. In other embodiments, the sizeof the conductive portion 118 may be adjustable. For example, in oneembodiment, wherein the probe 100 includes a conductive shaft 122 withan electrically insulative sheath or coating 116 disposed thereon, theelectrically insulative sheath 116 may be structured such that it may beslid or otherwise moved distally or proximally along the shaft 122.Thus, when the electrically insulative sheath 116 is moved proximallyalong the shaft 122, the electrically exposed portion 118, or activeelectrode, would become longer. When the electrically insulative coating116 is moved distally on the shaft 122, the active electrode 118 wouldbecome shorter. As mentioned above, altering the length of the activeelectrode 118 may affect the geometry of a lesion formed therefrom. Insome embodiments, the length of the active electrode 118 may be modifiedbefore, during or after a treatment procedure while, in otherembodiments, the length of the active electrode 118 may not be modifiedduring the actual course of the procedure. For example, in one suchembodiment, the probe 100 may have a safety mechanism, for example astopping means such as a clamp, to prevent movement of an insulativesheath 116 during the course of a treatment procedure.

In another alternate embodiment of the present invention, a treatmentapparatus can include an introducer 604 (see FIG. 6) in addition to aprobe. The introducer may be used to deliver energy to the patient'sbody, as will presently be described, and/or the introducer may be usedto facilitate insertion of the probe, as will be described below. Inembodiments wherein the introducer is used to deliver energy, theintroducer can include at least one electrically exposed conductiveportion and at least one electrically insulated portion. In someembodiments, the body of the introducer may be constructed from aconductive material, which is at least partially overlain with aninsulating sheath or coating, defining the insulating region; however,in some embodiments, the introducer may be constructed from aninsulating material with one or more conductive bodies or electrodesapplied externally. The distal end of the introducer may be pointed orsharp. For example, the distal end of the introducer can include abevel. In one embodiment, the at least one electrically insulatedportion may extend from the proximal region of the introducer to thedistal end of the introducer, such that the distal face of theintroducer includes at least one exposed conductive portion. Inembodiments comprising a bevel, the at least one exposed conductiveportion can include the bevel. In alternate embodiments, the exposedconductive portion may, alternatively or in addition, be located on aside of the introducer. In some embodiments, the electrical insulationmay extend to the heel of the bevel of the introducer, while in others,the insulation may end further proximally along the introducer.

In some embodiments, the introducer is straight, whereas in some otherembodiments the introducer may be bent. For example, in some suchembodiments, the introducer may have about a 5° to about a 20° bend inthe distal region of the introducer. In some embodiments, the introducermay be between about 16 and about 18 AWG, between about 75 and about 150mm in length, with the electrically exposed conductive portion about 2mm to 6 mm in length. In these embodiments, the probe may be structuredto be disposed within the lumen of the introducer and to be inelectrical contact with the introducer when fully disposed within theintroducer.

The probe can include an electrically conductive elongated shaft, aconnecting means for connecting to an energy source, and a connectingmeans for connecting to a cooling supply, for example as describedherein above. Thus, when energy is supplied by an energy source to theprobe, the energy flows along a conductive portion of the introducer andis delivered to the target treatment site, traveling through the tissueor body to a reference or return electrode. In such embodiments, theshaft of the probe may be electrically conductive and exposed alongsubstantially the entire length of the probe. In other words, a probeused in such an embodiment in conjunction with an introducer may notinclude an electrically insulative coating as described above.

In some embodiments, the distal end of the probe may be substantiallyflush with the distal end of the introducer when fully disposed in theintroducer. In other embodiments, the distal end of the probe may extenddistally from the distal end of the introducer when fully disposed inthe introducer. In other embodiments, the distal end of the elongatemember may be recessed proximally from the distal end of the introducerwhen fully disposed in the introducer. As used herein, the phrase “fullydisposed” refers to a first member being substantially fully receivedwithin a second member such that, under normal use, it is not intendedto be inserted into the second member any further.

The probe and the introducer may be structured such that when the probeis fully positioned inside or disposed within the introducer, at least aportion of the probe is in electrical and/or thermal contact with atleast a portion of the introducer, such that thermal and/or electricalenergy may be delivered from the probe to the introducer. This may beaccomplished by flushing the introducer with a liquid such as salineprior to inserting the probe, such that a layer of liquid remainsbetween at least a portion of the probe and the introducer. The salinemay then serve to conduct electricity and/or heat between the probe andthe introducer. Alternatively, the probe and introducer may bestructured such that they are in physical contact when the probe isfully disposed within the introducer, thereby also being in electricaland thermal contact. In a further embodiment, a portion of the probe maybe in thermal contact with the conductive portion of the introducer.This may be beneficial in that the cooling of the probe would allow forthe conductive portion of the introducer to be cooled. The probe may becooled by a variety of methods, as described above.

Embodiments comprising a cooled probe within an introducer may beadvantageous in that pre-existing introducers may be used in conjunctionwith such embodiments of a cooled probe. Thus, these probe embodimentsmay allow for use of an introducer that is similar to those currently inuse and familiar to practitioners, but which can be used to createlarger lesions than presently possible due to the cooling supplied tothe probe disposed within the introducer and which can deliver liquid tothe target site without removal of the probe due to the arrangement ofthe T-joint including the liquid delivery side port, as described belowwith respect to FIGS. 20 and 21. In addition, practitioners may befamiliar with a procedure involving positioning the distal region of anintroducer at a target site, positioning a probe within the introducer,and delivering energy from the probe to the introducer, and from theintroducer to the target site. Thus, a cooled probe of this embodiment,sized to be disposed within an introducer, would allow practitioners tofollow a normal procedure with the added benefit of cooling, similar towhat they have previously practiced using a similar introducer thoughwithout cooling. In still other embodiments, the side port can be partof the introducer itself, as described below with respect to FIGS.17-18.

With reference now to FIG. 6, systems of the present invention caninclude one or more of: one or more probes 100; one or more introducerapparatuses 604; one or more obturator apparatuses 606; one or moredispersive return electrodes (not shown); one or more sources of coolingas discussed above; one or more energy sources, for example generators608; and one or more connecting means, for example cables 612.

The introducer apparatus may aid in inserting the probe 100 into apatient's body. The introducer apparatus can include a hollow elongateintroducer 604 and an obturator 606. In this embodiment, as mentionedabove, the introducer 604 may be useful for facilitating insertion ofthe device into the patient's body. For example, the introducer 604and/or the obturator 606 may be substantially stiff or rigid, such thatthe introducer apparatus may assist in piercing skin or other bodytissues. The obturator 606 may be structured to cooperatively engage theintroducer 604. In other words, the obturator 606 may be sized to fitwithin the lumen of the introducer 604 and can include means forsecuring the obturator 606 to the introducer 604. In one embodiment,when the obturator 606 is fully disposed within the introducer 604, theobturator 606 sufficiently occludes the lumen of the introducer 604 suchthat tissue is prevented from entering the lumen when the introducerapparatus is inserted into the body. In some embodiments the distal endof the obturator 606 may be sharp or pointed. In these embodiments, thedistal end of the obturator 606 may be conical, beveled, or, morespecifically, tri-beveled. The lengths of the obturator 606 and theintroducer 604 may vary depending on the application. In one embodiment,the introducer 604 may be sized such that its distal end can reach thetarget tissue within the body while the proximal end remains outside ofthe body. In some embodiments, the introducer 604 can be between about5.5 inches (13.97 cm) and about 7.5 inches (19.05 cm) in length, andobturator 606 may be between about 5.5 inches (13.97 cm) and about 7.5inches (19.05 cm) in length. More specifically, the introducer 604 maybe about 6.4 inches (16.26 cm) in length, and the obturator 606 may beabout 6.6 inches (16.76 cm) in length. The obturator 606 may be slightlylonger than the introducer 604, so that the distal end of the obturator606 may protrude from the introducer 604 when fully disposed. In someembodiments, obturator 606 may be substantially longer than theintroducer 604, and may be visible under fluoroscopy, such that it mayaid in visualizing the location of lesion formation when a cooled probeis used. Further details regarding this embodiment are disclosed in U.S.Patent Application Publication No. 2009/0024124 to Lefler, et al., whichis incorporated herein by reference. The lumen of the introducer 604 canalso be sized to accommodate the diameter of the probe 100, whileremaining as small as possible in order to limit the invasiveness of theprocedure. In a specific embodiment, the proximal regions of theintroducer 604 and the obturator 606 are structured to be lockedtogether with a hub or lock.

In one embodiment, introducer 604 and the obturator 606 can be made fromstainless steel. In other embodiments, the introducer 604, the obturator606, or both may be made from other materials, such as nickel-titaniumalloys for example. Furthermore, in some embodiments, the obturator 606can include a means for connecting the obturator 606 to the generator608, for example a wire or cable. In such embodiments, the obturator 606may be operable to measure the impedance of tissue as the introducerapparatus is inserted into the patient's body. In addition oralternatively, the obturator 606 may be operable to deliver stimulationenergy to a target tissue site, as described further herein below.

In some embodiments, the probe 100 may be structured to be operativelyconnected to an energy source 608, for example a generator 608. Theconnecting means 612 for connecting the probe 100 to the generator 608can include any component, device, or apparatus operable to make one ormore electrical connections, for example an insulated wire or cable. Inone embodiment, the connecting means 612 can include an electrical cableterminating at the hub 114 as well as a connector at a proximal endthereof. The connector may be operable to couple to the energy source608 directly or indirectly, for example via an intermediate cable. Atleast one wire or other electrical conductor associated with the cable612 may be coupled to a conductive portion of the shaft 122, for exampleby a crimp or solder connection, in order to supply energy from theenergy source 608 to the shaft 122. In one specific embodiment, a 4-pinmedical connector may be used to connect the cable 612 to anintermediate cable (not shown), which may be further attached to a14-pin connector capable of being automatically identified whenconnected to the generator 608.

The generator 608 may produce various types of energy, for examplemicrowave, ultrasonic, optical, or radio-frequency electrical energy. Insome embodiments, generator 608 may produce radiofrequency electricalcurrent, having a frequency of between about 10 kHz and about 1000 kHz,at a power of between about 1 Watts and about 50 Watts. In someembodiments, the generator 608 can include a display means incorporatedtherein. The display means may be operable to display various aspects ofa treatment procedure, including but not limited to any parameters thatare relevant to a treatment procedure, such as temperature, power orimpedance, and errors or warnings related to a treatment procedure.Alternatively, the generator 608 can include means for transmitting asignal to an external display. In one embodiment, the generator 608 maybe operable to communicate with one or more devices, for example withone or more probes 100 and/or one or more sources of cooling, forexample pumps 610. Such communication may be unidirectional orbidirectional depending on the devices used and the procedure performed.An example of an RF generator that may be used as part of a system ofthe present invention is the Pain Management Generator (PMG) of BaylisMedical Company Inc. (Montreal, QC, Canada). Further details regardingembodiments of energy sources are disclosed in U.S. Pat. No. 8,882,755to Leung, et al. and U.S. Pat. No. 7,258,688 to Shah, et al., both ofwhich are previously incorporated herein by reference.

As an example of communication between the generator 608 and otherdevices in a system of the present invention, the generator 608 mayreceive temperature measurements from one or more temperature sensingdevices 112. Based on the temperature measurements, the generator 608may perform some action, such as modulating the power that is sent tothe probe(s). For example, power to the probe(s) could be increased whena temperature measurement is low or decreased when a measurement ishigh, relative to a predefined threshold level. If more than one probeis used, the generator may be operable to independently control thepower sent to each probe depending on the individual temperaturemeasurements received from the temperature sensing devices associatedwith each probe. In some cases, the generator 608 may terminate power toone or more probe(s) 100. Thus, in some embodiments, the generator 608may receive a signal (e.g., temperature measurement) from one or moreprobe(s), determine the appropriate action, and send a signal (e.g.,decreased or increased power) back to one or more probe(s). In addition,when using more than one probe 100, in embodiments where the generator608 does not control each of the probes 100 independently, the averagetemperature or a maximum temperature in the temperature sensing devices112 associated with probe(s) 100 may be used to control the coolingmeans.

In some embodiments, systems of the present invention can include oneprobe; in other embodiments, systems of the present invention caninclude a plurality of, for example two, probes. The system may beoperated, for example, in a monopolar mode, a bipolar mode, or amultiphasic/multi-polar mode. When operated in a monopolar mode, anynumber of probes may be used, and the system may further include adispersive return electrode. The dispersive return electrode may be, forexample, a grounding pad for attaching to the patient's skin, or may bea substantially large electrode that is integral with the probe 100.When the system is operated in a bipolar mode, any number of probes, forexample two probes, may be used, and current may travel between theprobes. Alternatively, when one probe is used, current may travelbetween a conductive portion 118 and a second electrically conductiveand exposed portion on the probe 100. For example, the probe 100 caninclude a second electrically conductive and exposed portion in the formof a ring that is disposed around probe 100 at a location proximal tothe conductive portion 118. The conductive portion 118 and the secondelectrically conductive and exposed portion may be electrically isolatedfrom each other, and the probe 100 can include means for operativelyconnecting the second electrically conductive and exposed portion to asource of energy which is at a different electrical potential than theelectrode 118, or to a circuit ground.

The operation of the system may be manually controlled by a user, or maybe automatically controlled based on certain parameters, for example,based on a measurement of a property of a component of is the systemitself or of a property of the tissue being treated. When more than oneprobe is used, means of controlling the operation of the system may beconfigured to independently control each probe such that, for example,current flow to any of the probes may be independently adjustable. Inembodiments of a system having automatic control, the system can includea controller operable to control one or more devices based on specifiedcriteria. Further details regarding automatic or manual control of thesystem are provided in U.S. Pat. No. 8,882,755 to Leung, et al.

Regardless of the various features described above and referring now toFIGS. 17 to 21, the electrosurgical device contemplated by the presentinvention can, in some embodiments, include a side port 224 or 406 forthe introduction of liquid into a lumen 208 defined by an outer diameter202 of the probe 100, 100A-F, 200, or 400 and an inner diameter 204 ofthe introducer 604 (also having an outer diameter 206) when the probe100, 200, or 400 is positioned inside the introducer 604 such that adistal end 106 of the probe 100, 200, or 400 can contact a target site(e.g., the site near or adjacent tissue to be treated). FIG. 19 shows across-sectional view of the lumen 208 defined by the inner diameter 204of the introducer 604 and the outer diameter 202 of the electricallyinsulated portion 116 of the probe 200 at cut line 2C. The side port canbe connected to a syringe 222 or other suitable liquid introductionapparatus (e.g., an IV bag, etc.) via tubing 220 so that a liquidcontaining a therapeutic agent, saline, etc. can be injected into thelumen 208 and can exit the distal end 214 of the introducer 604 at ornear the target site at liquid exit 230 to bathe an exposed conductiveportion 118 of the probe 100, 200, or 400 and the surrounding tissuewith the liquid. The side port 224 or 406 can be a component of theintroducer hub 210 as shown in FIGS. 17 and 18 or can be disposedbetween the introducer 604 and the probe 200 as a component of a T-joint402 as shown in FIGS. 20 and 21. Further, a seal 216 can be formedbetween the proximal region 108 of the probe 200 or 400 and theintroducer hub 210 near the proximal end 212 of the introducer 604 or atthe T-joint 402 to prevent the backflow of liquid from the side port 224or 406 to the proximal region 108 of the probe 200 or 400. Additionally,the syringe 222 can be removed from the tubing 220 so that the tubing220 can serve as a vent 218 at its open end during treatment with theelectrosurgical device, which can, in addition to the cooled probe,reduce the temperature of tissue at the target site, thus minimizingtissue damage.

In one particular embodiment, as shown in FIGS. 17 and 18, theelectrosurgical device includes a probe 200 and an introducer 604 thatdefine a lumen 208 for the exit of liquid from the distal end 214 of theintroducer 604 at liquid exit 230 to bathe an exposed conductive portion118 of the probe 200 and the surrounding tissue (i.e., the target site)with a liquid-based therapeutic agent, saline, or any other suitableliquid. In order to prevent the back flow of liquid, a seal 216 isformed between a proximal region 108 of the probe 200 and a proximal end212 of the introducer 604 at hub 114, which also locks the proximalregion 108 of the probe 200 in place with respect to the introducer hub210. The introducer hub 210 also defines a void 226 in which liquid canbe injected from a syringe 222 or any other suitable liquid introductiondevice via tubing 220 that is connected to a side port 224 that isformed in the introducer hub 210. The liquid can then flow in the lumen208 formed between the inner diameter 204 of the introducer 604 at itsdistal end 214 and the outer diameter 202 of the electrically insulatedportion 116 of the probe 200. Such an arrangement prevents having toremove the probe 200 from the introducer 604 in order to inject atherapeutic agent or other suitable liquid to the target site or nearbytissue. Further, after the therapeutic agent or other suitable liquidhas been delivered to the target site, the syringe 222 or other suitableliquid introduction device can be removed so that the resulting open endof the tubing 220 can serve as a vent 218 during treatment, which, inconjunction with probe 200 cooled via the means discussed above, cancool the tissue near the target site to minimize tissue damage.

In another particular embodiment, as shown in FIGS. 20 and 21, theelectrosurgical device also includes a probe 400 and an introducer 604that define a lumen 208 for the exit of liquid from the distal end 214of the introducer 604 at liquid exit 230 to bathe and exposed conductiveportion 118 of the probe 200 and the surrounding tissue (i.e., thetarget site) with a liquid-based therapeutic agent, saline, or any othersuitable liquid. In order to prevent the back flow of liquid, a seal 216is formed between a proximal region 108 of the probe 200 and a T-joint402, where a hub 114 locks the proximal region 108 of the probe 200 inplace with respect to T-joint 402. The T-joint 402 also defines a void226 in which liquid can be injected from a syringe 222 or any othersuitable liquid introduction device via tubing 220 that is connected toa side port 406 that is formed in the T-joint 402. The liquid can thenflow in the lumen 208 formed between the inner diameter 204 of theintroducer 604 at its distal end 214 and the outer diameter 202 of theelectrically insulated portion 116 of the probe 200, where the introduce604 is secured to the T-joint 402 via a hub 404. Such an arrangementprevents having to remove the probe 200 from the introducer 604 in orderto inject a therapeutic agent or other suitable liquid to the targetsite or nearby tissue. Further, as with the embodiment discussed abovewith respect to FIGS. 17 and 18, after the therapeutic agent or othersuitable liquid has been delivered to the target site, the syringe 222or other suitable liquid introduction device can be removed so that theresulting open end of the tubing 220 can serve as a vent 218 duringtreatment, which, in conjunction with probe 200 cooled via the meansdiscussed above, can cool the tissue near the target site to minimizetissue damage.

Generally speaking, the lumen 208 defined by an outer diameter 202 ofthe probe 100, 200, or 400 and an inner diameter 204 of the introducer604 (also having an outer diameter 206) when the probe 100, 200, or 400is positioned inside the introducer 604 may have a cross-sectionperpendicular to a longitudinal axis in the form of an annular ringdefining a space having a thickness or width of from about 0.00175inches (0.045 millimeters) to about 0.003 inches (0.076 millimeters).Desirably, this thickness or width may be from about 0.002 inches (0.051millimeters) to about 0.00285 inches (0.072 millimeters). Moredesirably, this thickness or width may be from about 0.0025 inches(0.064 millimeters) to about 0.00275 inches (0.07 millimeters).

While the volume of liquid that may be delivered to the target site overa time period of about 30 seconds may be up to about 2 milliliters, moredesirably, the volume of liquid delivered to the target site over a timeperiod of about 30 seconds ranges from about 0.05 milliliters to about0.75 milliliters. Even more desirably, the volume of liquid delivered tothe target site over a time period of about 30 seconds ranges from about0.1 milliliters to about 0.5 milliliters. For example, the volume ofliquid delivered to the target site over a time period of about 30seconds may be about 0.25 milliliters to about 0.35 millilitersdelivered to the target site over about 30 seconds. These valuesgenerally apply to delivery of liquids having a viscosity of rangingfrom about 0.75 centipoise to about 3 centipoise (e.g., about 1centipoise) at room temperature (e.g., about 20° C.).

The lumen 208 may be sized to accommodate a liquid delivery rate of fromabout 0.001667 milliliters per second to about 0.0667 milliliters persecond without creating significant pressure build-up or flowrestrictions. When the liquid delivery flow rate is divided by thecross-sectional area of the lumen (e.g., fluid delivery channel), theresult is a liquid velocity. For example, the lumen 208 may provide aliquid velocity of from about 14 inches per minute to about 436 inchesper minute or from about 0.23 inches per second to about 7.3 inches persecond, which corresponds to a liquid velocity of from about 5.8 mm/secto about 185 mm/sec. Desirably, the liquid velocity may be from about 25mm/sec to about 85 mm/sec.

Having a ratio of liquid delivery flow rate to cross-sectional area inthis range can be advantageous for lumen cross-sectional areas in therange of about 0.0001 square inch (0.065 mm²) to 0.0003 square inch(0.194 mm²) because it is important to minimize the cross sectional areaof the lumen in order to maximize the outer diameter of the probe 100without interfering with liquid delivery through the lumen 208 definedby an outer diameter 202 of the probe 100, 200, or 400 and an innerdiameter 204 of the introducer 604. This configuration is particularlyadvantageous for cooled probes because the overall diameter of the probeand introducer combination can be reduced while still allowing liquiddelivery because it eliminates the need for a separate lumen or channelthat extends internally through the probe to an aperture at the distalend or region of the probe to provide for liquid delivery.

In general, embodiments of a method of the present invention involveusing a treatment device, for example a probe, in a particular region ofa patient's body to form a lesion of sufficient size and suitablegeometry to effectively treat the target tissue. For example, in onebroad aspect, a method is provided for creating a lesion at a targetsite within a body of a human or animal using an electrosurgical devicehaving a longitudinal axis.

The desired size and geometry of the lesion may depend on the specificanatomy and tissue being targeted and may be affected by severalparameters as described herein, including but not limited to thegeometry of the treatment device and the amount of cooling delivered tothe treatment device. Thus, in accordance with one aspect of the presentinvention, steps are provided for creating a lesion with desiredcharacteristics during the course of an electrosurgical procedure. Thelesion may function to inhibit neural activity, for example nociception.Alternatively, in some embodiments, the lesion may have other effects,for example the shrinkage of collagen. Method embodiments of the presentinvention can generally include one or more of the steps of: determininga desired lesion shape, size, and location; selecting an electrosurgicalinstrument or device, for example a probe, and energy deliveryparameters, for example voltage, based on the desired lesion shape,size, and location; inserting the electrosurgical instrument or deviceinto a patient's body; positioning the electrosurgical instrument ordevice at a target site; delivering energy, for example radiofrequencycurrent, through the electrosurgical instrument or device to the targetsite to form a lesion; and applying cooling to the electrosurgicalinstrument or device. As will presently be discussed, embodiments of themethod aspect of the present invention may be useful, for example, toallow for more straightforward device placement during electrosurgicalprocedures than is presently possible.

In one embodiment of the method aspect of the present invention, thestep of inserting an electrosurgical instrument or device can includeinserting a probe percutaneously into a patient's body, and the step ofpositioning an electrosurgical instrument or device can includeadvancing the electrosurgical instrument or device until the activeelectrode is at or in the vicinity of a target treatment site. The stepof inserting a probe may optionally be preceded by one or moreadditional steps including, for example, inserting an introducerapparatus into the body in the vicinity of the target treatment site,measuring one or more properties of a device or of tissue at or near thetarget treatment site, inserting or removing material at or near thetarget treatment site, and performing another treatment procedure at ornear the target treatment site.

As described above, in some embodiments, the probe may be used inconjunction with an introducer apparatus, which can include anintroducer and an obturator, for example. In use, the obturator may beinitially disposed within a lumen of the introducer to facilitateinsertion of the introducer apparatus to the target treatment site. Oncethe introducer apparatus has been properly positioned, the obturator maybe removed and replaced within the introducer lumen by the probe. Insome embodiments, as described further herein below, the obturator maybe operable to measure the impedance of tissue as the introducerapparatus is inserted into the patient's body, which may assist inpositioning the introducer apparatus at the target site. Alternativelyor in addition, the obturator may be operable to deliver stimulationenergy to the target treatment site, as described below. The probe andintroducer may be structured such that when the probe is fully disposedwithin the introducer, the distal end of the probe may be aligned withthe distal end of the introducer. In other embodiments, the probe andthe introducer may be structured such that when the probe is fullydisposed within the introducer the distal end of the probe protrudes orextends from the distal end of the introducer. For example, as describedabove, if the introducer includes an electrically conductive elongatemember covered by electrically insulating material, with a distalportion that is electrically conductive and exposed, then the probe maybe operable to deliver energy from an energy source to the conductivedistal portion of the introducer. This delivery of energy may befacilitated by physical contact between the tip of the probe and theinner surface of the introducer. In such an embodiment, the probe tipmay be aligned with the distal end of the introducer and the length ofthe exposed conductive portion of the introducer will affectcharacteristics of the resulting lesion, as has been described abovewith reference to FIG. 5. Alternatively, in some embodiments, theintroducer can include an electrically insulated elongate member nothaving a conductive and exposed distal portion. In such embodiments, thedistal end of the probe may protrude or extend from the distal end ofthe introducer and the distance that the probe tip extends may bealtered by advancing or retracting the probe. The distance that theprobe tip extends from the introducer will affect the formation of thelesion, as described above.

During the steps of inserting and positioning the probe, the probe maybe inserted and positioned such that the distal end of the probe,comprising the active electrode, is the portion of the probe that isclosest to the treatment site. If the treatment site includes a surface,for example, the probe may be inserted and positioned substantiallyperpendicular or generally upstanding to the surface, for example at anangle between about 80° and about 100° relative to the surface. In otherembodiments, the probe may be positioned at an angle between about 45°and 135° or, in alternate embodiments, between about 60° and 120°. Theprobe may be inserted and positioned such that the distal end of theprobe is directly adjacent to, or in contact with the target treatmentsite, or may be inserted and positioned such that the distal end of theprobe is proximal to the target site. For example, in one embodiment, aprobe may be inserted and positioned using what may be described as a“perpendicular” or “gun-barrel” approach. In this embodiment, the probemay be directed to the target site such that its longitudinal axis issubstantially perpendicular or generally upstanding to the line or planeformed by the target tissue or site. For example, if the target tissueis a nerve, the probe may be positioned such that the probe issubstantially perpendicular or generally upstanding relative to thenerve. If the target tissue includes more than one neural structure,such as a nerve or nerve branch, the probe may be inserted andpositioned such that it is substantially perpendicular or generallyupstanding to a plane containing the neural structures. As will bedescribed in more detail below, embodiments of the present invention mayallow for the creation of a lesion that is located primarily distallywith respect to the distal end of a probe, thus allowing a probe thathas been inserted substantially perpendicularly or generally upstandingrelative to a target site to effectively treat the target site bydelivering energy to form a lesion distal to the probe.

In alternate embodiments, the probe may be inserted at various angles tothe target treatment site, depending on the procedure being performedand the anatomical structures involved. For example, in someembodiments, the probe may be inserted such that it is substantiallyparallel to a target nerve, for example at an angle of between about 0°and about 20°. In other embodiments, the probe may be inserted such thatit is at an angle of between about 20° to about 70° to the target site.In general, embodiments of the present invention allow for variousangles of approach by providing an apparatus and method of use thereoffor creating a lesion of variable size and at various locations relativeto the apparatus.

The step of inserting and positioning a probe may involve the insertionof a single probe to a location in the vicinity of a single targettreatment site, the insertion of multiple probes in the vicinity of asingle target treatment site, or the insertion of multiple probes tomultiple locations in the vicinity of multiple target treatment sites.The probe or probes may be configured to deliver energy in a monopolar,bipolar or multi-polar configuration. If the probe or probes areconfigured to deliver energy in a monopolar configuration, the method ofthe current invention may also include a step of placing a referenceelectrode, such as a grounding pad, at another location on or in thebody. The steps of inserting and positioning a probe may optionally befollowed by any number of steps, for example prior to the commencementof the step of delivering energy including, but not limited to, one ormore of: measuring one or more properties of a device or of tissue at ornear the target treatment site; applying a stimulation signal to atissue (for example, neural tissue) at or near the target treatmentsite; measuring the reaction to stimulation (for example, thesomato-sensory evoked potential, or SSEP) of a tissue (for example,muscular or neural tissue) in response to the application of astimulation signal at or near the target treatment site; inserting orremoving material at or near the target treatment site; and performinganother treatment procedure at or near the target treatment site.Further details regarding these steps may be found in U.S. Pat. No.8,882,755 to Leung, et al., U.S. Pat. No. 7,819,869 to Godara, et al.,U.S. Pat. No. 8,951,249 to Godara, et al., U.S. Patent ApplicationPublication No. 2006/0259026 to Godara, et al., and U.S. Pat. No.8,096,957 to Conquergood, et al. Following the performance of one ormore of the above optional steps, one or more probes may be reinserted,moved, or otherwise repositioned and any optional steps may then berepeated.

The step of delivering energy to the target treatment site, for exampleto create a lesion at the target treatment site, may involve thecreation of a lesion of a desired shape and at a desired locationrelative to the probe. As mentioned hereinabove, lesion shape andlocation may be affected by the length of the exposed distal end of theprobe. The less of the probe that is exposed, the more distally,relative to the probe, the lesion will form. In addition, the shape ofthe lesion will be generally more spherical if less of the tip isexposed. For example, if the exposed length of the distal end is limitedsubstantially to the distal-most hemisphere (i.e., the face) of the tip,then a substantially spherical lesion may form primarily distally withrespect to the probe. Such a probe may be positioned such that theactive electrode of the probe lies substantially proximal from thetarget site, for example a nerve. Energy may then be delivered to theprobe such that a lesion may form substantially distal to the activeelectrode of the probe. Conversely, if more of the tip is exposed, thenthe lesion will appear more oblate and may form more radially (i.e.perpendicular to the longitudinal axis of the probe) around the distalend and the component of the lesion distal to the distal end willdecrease.

The type, parameters, and properties of the energy delivered to theprobe may vary depending on the application, and the invention is notlimited in this regard. The energy may be one of various types ofenergy, for example electromagnetic, microwave, or thermal. In someembodiments, radiofrequency electrical current having a frequency ofbetween about 10 kHz and about 1000 kHz, at a power of about 50 Watts,may be delivered to the probe.

In some embodiments of the method of the present invention, the step ofdelivering energy to the tissue may be preceded by, and/or donecoincidently with, a step of utilizing a cooling or heat transfer systemas discussed above with respect to FIGS. 3A-3F. Cooling may be used toreduce the temperature of the tissue in the vicinity of the site ofenergy delivery, allowing more energy to be applied without causing anincrease to an unsafe temperature in local tissue. The application ofmore energy allows regions of tissue further away from the electrode(s)to reach a temperature at which a lesion can form, thus increasing themaximum size/volume of the lesion. Furthermore, depending on thestructure of the probe, cooling may allow for a lesion to form at aposition that is substantially distal to and, in some embodiments,spaced from the probe. Further details regarding cooled probes aredisclosed in U.S. Patent Application Publication No. 2007/0156136 toGodara, et al. and U.S. Pat. No. 7,819,869 to Godara, et al., both ofwhich are incorporated herein by reference. Thus, cooling anelectrosurgical probe may change the size, shape, and location offormation of a lesion. As noted above, the theory described hereinregarding tissue heating and lesion formation is not intended to limitthe present invention in any way.

In one embodiment, a step of applying cooling (or, in other words,removal of energy in Watts) may be used to facilitate the creation of alesion that is distal to the probe 100 and which is spaced from theprobe 100, as shown in FIG. 7. As long as a sufficient amount of coolingis applied to maintain the temperature of the tissue surrounding thedistal end 106 of the probe 100 below the temperature at which a lesionwill form (approximately 42° C.), a sufficient amount of power may besupplied from an energy source to create a lesion at some distance awayfrom, for example distal to, the probe 100. The distance of the lesionfrom the probe 100 may depend on the amount of cooling delivered. Forexample, as shown in FIG. 7, if a relatively low amount of cooling issupplied (LC), the lesion may be relatively close to the probe 100. If ahigher amount of cooling is supplied (HC), the lesion may form furtheraway from the probe, where a medium amount of cooling (MC) results in alesion formed in a space in between. This application of the method ofthe present invention may be used in cases where the target treatmentsite is not directly accessible by the probe, for example where thetarget site includes, lies within, or is disrupted by a crevice,fissure, or other uneven surface feature. As discussed previously, theapplication of cooling can be used to allow the creation of a lesion ina region of tissue further from the probe than might be possible withoutcooling. Cooling can thus be used to control the position of a lesionmore precisely, with increased cooling allowing the creation of a lesionfurther from the probe.

Additionally, cooling may be modulated during energy delivery (and insome cases, accompanied by modulation of energy delivery) as follows:energy may be delivered initially in conjunction with cooling so that alesion begins to form at some distance distally spaced apart from theprobe; cooling may then be reduced, causing the lesion to extend atleast partially in the direction of the probe. Thus, a further aspect ofsome embodiments of the method aspect of the present invention involvesthe control of cooling parameters in order to create a lesion at adesired location relative to the probe. As has been mentioned withrespect to adjusting the exposed length of the distal end, coolingparameters may be adjusted before, during or after energy delivery.

Thus, the methods contemplated by the present invention provide forcreating a lesion having a desired shape, size and location based on oneor more factors, including, but not limited to, probe geometry anddegree of cooling. The desired lesion parameters may be determined by auser in advance of a treatment procedure based, in some embodiments, onthe specific tissue being targeted, as well as individual patientanatomy. For example, in procedures wherein the target site forformation of a lesion is located within a fissure, groove, or rut in abone, it may not be possible to position the probe at the target site,and thus it may be desired to position the probe 100 at a locationspaced from the target site. In this case, the user may select a probe100 wherein the electrically exposed conductive portion 118 includesonly the distal face 107 of the probe 100, and may select a high flowand/or low temperature of cooling fluid. Such a configuration may allowfor the formation of a lesion distal to the probe tip 118, thus allowingthe probe tip/electrode/conductive portion 118 to be located at somedistance from the target site. If the probe 100 is positionedsubstantially perpendicular to the target site, a lesion may form at alocation distal to the distal end of the probe (i.e., within the fissurein the bone). In another example, the target site may be directly on thesurface of a bone. In this case, the user may select a probe 100 whereinthe conductive portion 118 extends along the shaft proximally from thedistal end, and may select a moderate or low amount of cooling. The usermay position the distal end of the probe adjacent to the target site,for example about 0.1 mm to about 3 mm from the target site, or mayallow the distal end of the probe 100 to touch the bone, and may orientthe probe such that the longitudinal axis of the probe 100 issubstantially perpendicular to the bone. In this case a lesion may formaround the conductive portion of the probe 100, and between the distalend of the probe 100 and the bone. Alternatively, the aforementionedprobe 100 having an electrode 118 comprising only the exposed distalface 107 may be used in this case as well. In both of these examples, aprobe 100 with an adjustable insulating sheath may be used to provide anappropriately sized exposed the electrode 118 to produce the desiredlesion. Alternatively, as mentioned hereinabove, the position of a probewithin an introducer may be altered by advancing and/or retracting theprobe to provide an appropriately sized exposed the electrode 118 toproduce the desired lesion.

In some embodiments, two cooled probes 100 in a bipolar configurationmay be used, which may allow for the creation of a substantially uniformlesion between the electrodes 118 of the two probes 100. This concept isillustrated in FIG. 8A, showing a graph of temperature vs. distance in atissue with uniform thermal/electrical properties. The electrodes 118 ofthe two probes 100 are located at positions p1 and p2 on the x-axis andthe temperature needed to create a lesion is noted as T_(LES) on they-axis. In FIGS. 8A and 8B, solid lines 802 and 804 represent a cooledprobe assembly, while dashed lines 801 and 803 represent a non-cooledprobe assembly. Without the benefits of cooling, the higher the powerthat is supplied to the electrodes 118, the higher the temperaturearound the electrodes 118 will be. Curve 801 shows a temperatureprofile, as may be typically achieved using non-cooled probes in auniform tissue. In such a configuration it is difficult to create alesion extending from p1 to p2 because by supplying a large amount ofpower to the electrodes 118, the temperature at the locations p1 and p2of the electrodes reaches very high levels. High temperatures at theelectrodes may cause nearby tissue to char and possibly adhere to distalregions 104. Furthermore, raising the temperature of tissue causes theimpedance of the tissue to increase and limits the penetration ofcurrent into the tissue, thereby limiting the size of the lesion thatcan be created. In contrast, cooled probe assemblies may be used to forma desired lesion between p1 and p2 while reducing such temperatureeffects. Curve 802 shows a typical temperature profile for a uniformtissue as may be seen when using two cooled probe assemblies. Thetemperatures at the distal end regions, p1 and p2, are reduced relativeto the surrounding tissue due to the effect of the cooling. This allowsfor higher power to be transmitted to the electrodes 118 without concernfor tissue charring. In addition, because the temperature of tissuesurrounding the electrodes 118 is reduced, the impedance of thesurrounding tissue will not increase significantly and therefore currentsupplied by the electrodes 118 can penetrate more deeply into thetissue. As illustrated in FIG. 8A, a lesion can therefore be createdbetween p1 and p2 using cooled probes due to the lower localtemperatures at p1 and p2. Although FIG. 8A shows the temperature at p1and p2 to be below the lesioning temperature, the cooling supplied tothe cooled probes may be reduced or eliminated allowing the temperatureof tissue around p1 and p2 to increase in order to complete the lesionbetween p1 and p2.

In some embodiments, after the creation of a lesion, the probe 100 maybe repositioned, and energy may again be delivered in order to form afurther lesion. For example, after the formation of a first lesion, theprobe 100 may be withdrawn from the target site either partially orfully. In the case of partial withdrawal, energy may be delivered to thesite at which the probe 100 has been withdrawn to, such that a furtherlesion is formed. In the case of full withdrawal, the probe may bere-inserted and re-positioned at a second location, and energy may bedelivered to the second location to form a further lesion. The step ofrepositioning may be performed any number of times, to form any numberof lesions, as determined by a user. In embodiments comprising asteerable probe, the probe may be repositioned without withdrawing theprobe, by actuating the steering means associated with the probe.

Methods of the present invention may be used for various applications,including for the treatment of pain associated with many conditions.Examples of such conditions include, but are not limited to, ComplexRegional Pain Syndrome (CRPS), Trigeminal Neuralgia, Joint SpecificPeripheral Neuropathy, Facet Joint Pain, Intervertebral disc pain,Sacroiliac Joint Syndrome (SIJS) and Hypogastric or Pelvic Pain. Ingeneral, these conditions may be treated by affecting at least onetarget neural structure that may be associated with a patient's pain inaccordance with method embodiments of the present invention. Forexample, in the case of trigeminal neuralgia, embodiments of the presentinvention may be used to form a lesion at the trigeminal nerve. Someembodiments of a method of the present invention may also be used totreat further sources of pain, as will be described in more detailbelow.

In some embodiments, any or all of the method steps described above maybe performed with the aid of imaging. For example, the step of insertinga probe may be performed under X-ray fluoroscopic guidance. In a furtherembodiment, the imaging may be performed in a gun-barrel manner, whereinthe device is visualized along its longitudinal axis.

In some embodiments, rather than being delivered in a continuous manner,energy may be delivered in a series of amplitude or frequency modulatedpulses, whereby tissue heating is inhibited by interrupting periods ofenergy delivery with periods in which energy is delivered at a lowervoltage. In one specific embodiment, energy is delivered according to aset duty cycle of signal on time/off time, wherein the signal is “on”less than 100% of the time, as follows: during signal “on time” energyis delivered at a voltage that may beneficially be higher than voltagesthat can safely be used during continuous energy delivery (100% dutycycle) procedures; during signal “off time,” the heat generated in thevicinity of the probe may disperse throughout the tissue, raising thetemperature of tissue away from the probe, while tissue in the vicinityof the probe drops; energy is again applied and the delivery is cycledthrough “on time” and “off time” until a predetermined endpoint (e.g.,time or temperature) is reached or until a practitioner decides to endthe treatment. The reduction in temperature of tissue in the vicinity ofthe probe during signal “off time” may allow a higher voltage to be used(during “on time”), than would tend to be used in a continuous energydelivery procedure. In this way, the pulsing of energy delivery, eitherbetween signal “on time” and “off time,” as described above, or betweena higher voltage and a lower voltage (for example, a voltage capable ofgenerating a lesion in the tissue and a voltage not capable ofgenerating a lesion in the tissue, given the frequency of energy beingdelivered), the total amount of current deposited into the tissue may besufficient to create a larger lesion, at a further distance from theprobe, than would be possible using continuous energy delivery withoutmaintaining the tissue in the vicinity of the probe at a temperaturethat may cause charring.

As has been mentioned, a system of the present invention may be used toproduce a generally uniform or substantially homogeneous lesionsubstantially between two probes when operated in a bipolar mode. Incertain cases, generally uniform or substantially homogeneous lesionsmay be contraindicated, such as in a case where a tissue to be treatedis located closer to one active electrode than to the other. In caseswhere a uniform lesion may be undesirable, using two or more cooledprobes in combination with a suitable feedback and control system mayallow for the creation of lesions of varying size and shape. Forexample, preset temperature and/or power profiles that the procedureshould follow may be programmed into a generator prior to commencementof a treatment procedure. These profiles may define parameters (theseparameters would depend on certain tissue parameters, such as heatcapacity, etc.) that should be used in order to create a lesion of aspecific size and shape. These parameters may include, but are notlimited to, maximum allowable temperature, ramp rate (i.e., how quicklythe temperature is raised) and the rate of cooling fluid flow, for eachindividual probe. Based on temperature or impedance measurementsperformed during the procedure, various parameters, such as power orcooling, may be modulated, in order to comply with the preset profiles,resulting in a lesion with the desired dimensions. Similarly, it is tobe understood that a uniform lesion can be created, using a system ofthe present invention, using many different pre-set temperature and/orpower profiles which allow the thermal dose across the tissue to be asuniform as possible, and that the present invention is not limited inthis regard.

Embodiments of the method aspect of the present invention may be usefulfor creating a lesion having a desired shape, size and/or locationwithin various tissues of a human or animal. More specifically, someembodiments of the present invention can include treatment proceduresfor treating one or more target tissue sites associated with a patient'svertebral column. For example, treatment procedures may be performed atvarious locations external to the vertebrae, including but not limitedto target sites at the cervical, thoracic, lumbar and sacral regions ofthe spine. In addition, treatment procedures may be performed at targetsites within the vertebrae themselves, referred to as an intraosseousprocedure. Furthermore, treatment procedures may be performed at targetsites within one or more intervertebral discs. Although severalexemplary embodiments of such procedures will be presently described,the present invention is not limited to such procedures and may bepracticed at various target sites within a patient's body. In any or allof the embodiments disclosed herein, a treatment procedure can include astep of determining desired lesion parameters, including, but notlimited to, shape, size and location, and selecting probe geometry,location and cooling in order to create the desired lesion.

One application of an embodiment of a method of the present invention isfor the treatment of pain within or in the vicinity of an intervertebraldisc. As is disclosed in U.S. Pat. No. 6,896,675 to Leung, et al., andU.S. Pat. No. 6,562,033 to Shah, et al., U.S. Pat. No. 8,043,287 toConguergood, et al., U.S. Pat. No. 8,882,755 to Leung, et al., U.S.Patent Application Publication No. 2005/0277918 to Shah, et al., andU.S. Pat. No. 7,294,127 to Leung, et al., all of which are incorporatedherein by reference, RF energy may be delivered through a cooled probeto an intervertebral disc of a patient in order, for example, to treatpain. Treatment of an intervertebral disc may generally include thesteps of: inserting at least one probe into the intervertebral disc of apatient; and delivering energy through the probe(s) to the tissue of theintervertebral disc. As described above, the at least one probe may becooled and the degree of cooling may affect the size, shape and/orlocation of a lesion formed within the disc.

Referring to FIG. 9, the step of inserting at least one probe into anintervertebral disc 900 may proceed generally as follows (furtherdetails are provided in the aforementioned references): With a patientlying on a radiolucent table, fluoroscopic guidance may be used toinsert at least one probe towards the posterior of an intervertebraldisc. As mentioned above, the step of insertion can include the use ofan introducer apparatus, for example comprising an obturator/styletdisposed within an introducer. One method of accessing the disc is theextrapedicular approach, in which the introducer passes just lateral tothe pedicle, but other approaches may be used. In some embodiments, theintroducer apparatus may be advanced until the distal end of the styletpenetrates the annulus fibrosis 902 and enters the nucleus pulposus 904.In other embodiments, the introducer apparatus may be advanced until thedistal end of the stylet is within the annulus fibrosis 902. In furtherembodiments, the introducer apparatus may be advanced until the distalend of the stylet is proximal to, but not within, annulus fibrosis 902.In some particular embodiments, the stylet may be electrically connectedto the generator such that the stylet forms part of an impedancemonitoring circuit, as described above. In such embodiments, monitoringthe impedance may assist in positioning the introducer apparatus at adesired location, since different tissues may have different impedances.When the introducer apparatus has been positioned, the stylet may beremoved from the introducer. In some embodiments, a second introducerapparatus may then be placed contralateral to the first introducer inthe same manner, and the stylet may be removed. After removal of thestylet(s), the probe(s) may be inserted into the introducer(s), placingthe active electrodes in the disc such that the distance between activeelectrodes is, for example, about 1 mm to about 55 mm.

A method embodiment of the present invention may also be used to treatintraosseous target sites, i.e., target sites within a bony structure.Such procedures can be used to, for example, treat a tumor in the bonystructure or lesion a neural structure within the bone. In anintraosseous procedure, one or more introducers may generally be used togain access to the bone to be treated, for example, a vertebra of aspinal column. In such embodiments, the introducers can include a drillor other means for accessing the bone. Alternatively or in addition, ahammer or a reamer may be used to access an intraosseous site. As is thecase with procedures related to intervertebral discs, one or more probesmay be inserted at a site or sites within a bone and energy may bedelivered to active electrodes located at the distal regions of theprobes. Energy may be delivered in a bipolar mode, or in a monopolarmode. Furthermore, as mentioned above, one or more of the probes may becooled to allow for the formation of a lesion having a desired size,shape and location.

Another application of embodiments of the apparatus and method of thepresent invention is for the treatment of pain emanating from apatient's neck (i.e., the cervical region of the spine) as is disclosedin U.S. Patent Application Publication No. 2007/0156136 to Godara, etal.

Referring now to FIG. 10, a lateral view of the cervical region of thespine is shown. The cervical region of the spine generally includesseven cervical vertebrae and their associated zygapophyseal, or facet,joints. Nerves innervating the facet joints (FJ) are thought to beresponsible for certain types of neck/cervical pain. The cervical facetjoints are paired, synovial joints found along the back of the cervicalvertebral column at intervertebral levels C2-3 to C7-T1. The cervicalfacet joints (FJ) are planar joints formed between the inferiorarticular process (IAP) of one vertebra and the superior articularprocess (SAP) of the adjacent vertebra. Each articular process (AP)bears a circular or ovoid facet that is covered by articular cartilage,and each joint is enclosed by a fibrous joint capsule lined by asynovial membrane. The cervical facet joints are innervated by articularbranches derived from the medial branches of the cervical dorsal rami.The medial branches of the typical cervical dorsal rami curve mediallyand posteriorly as they exit the intervertebral foramen, hugging thearticular pillars. Articular branches arise as the nerve approaches theposterior aspect of the articular pillar. An ascending branch innervatesthe facet joint above, and a descending branch innervates the jointbelow.

A method of treating cervical/neck pain in accordance with oneembodiment of the present invention will be presently described. Thedescription will reference the anatomy of the facet nerve of the fourthcervical vertebra; however persons of skill in the art will recognizethat the method may be used to treat other nerves of other cervicalvertebrae as well, for example the third occipital nerve of the thirdcervical vertebra. Variations of the described method may be required inorder to accommodate anatomical differences of other cervical vertebrae.In some embodiments, the target site for treating cervical/neck pain caninclude the nerves innervating the facet joint. As describedhereinabove, these nerves may be located substantially adjacent to thearticular pillar of the cervical vertebra. Thus the target site (TS) forenergy delivery may be the region located slightly cephalad to thecentroid of the articular pillar, as shown in FIG. 10.

In one specific embodiment, the patient may be placed in the proneposition in preparation for the treatment procedure. The user mayoptionally administer various treatments, such as anesthetics orantibiotics, for example. The user may insert at least one probe, suchas probe 100 described hereinabove, percutaneously towards the targetsite. The step of inserting at least one probe can include the use of anintroducer apparatus, as described above. Such an apparatus may be anintroducer apparatus that includes an introducer 604 and an obturator606. The user may insert the introducer apparatus percutaneously intothe patient via a lateral approach, such that the longitudinal axis ofthe introducer is substantially perpendicular or generally upstanding,for example at an angle of about 80° to about 100°, relative to thetarget site (i.e., the centroid of the articular pillar). In otherwords, the longitudinal axis of the introducer may be substantiallyperpendicular or generally upstanding to the anterior-posterior (AP)axis of the body, as shown in FIGS. 11A-B, which show AP views of aportion of the cervical spine. In other embodiments, the probe may be atother angles relative to the AP axis of the body, for example betweenabout 45° and about 135°. In yet further embodiments, the probe may besubstantially parallel to the AP axis of the body. The insertion stepmay be facilitated with the use of fluoroscopic imaging techniques. Theuser may continue the insertion until a distal end of the introducerapparatus contacts the bony surface of the articular pillar, or may stopthe insertion when the distal end lies some distance, for example about2 to about 4 millimeters, proximal from the bony surface. In otherembodiments, the user may contact the bony surface of the articularpillar with the tip of the introducer, and may then retract theintroducer apparatus such that the distal end lies some distanceproximal from the surface, as has been described. Thus, depending on theconfiguration and positioning of the probe and/or introducer apparatus,the distal end of the probe may be in contact with the surface of thearticular pillar, or may be located some distance away from the bone.The position of the probe may be pre-determined based on the desiredlesion size, shape and location, as mentioned above. The position of theprobe may be verified using a variety of techniques, for example byusing fluoroscopic imaging. In some embodiments, the user may use depthstoppers to aid in the marking and/or maintaining the position of theintroducer apparatus within the patient's body.

When the introducer apparatus has been positioned, the user may withdrawthe obturator/stylet from the introducer, leaving the introducer inplace. Depending on the positioning of the introducer apparatus, thedistal end of the introducer may now be touching the bone, or may besome distance proximal from the bony surface, for example about 3 mmaway from the bone. The user may then insert a probe into the lumen ofthe introducer. The probe may be operatively connected to a source ofcooling fluid, for example pumps 610, and may further be operativelyconnected to a source of energy, such as generator 608, in order todeliver energy to the target site.

As described above, depending on the configuration and positioning ofthe probe, as well as the degree of cooling, the lesion formed at thetarget site may be of a variety of shapes and sizes, as described above.For example, as shown in FIG. 11A, the conductive portion 118 of theprobe can include substantially the distal face 107 of the probe. Thus,if the probe is sufficiently cooled, a lesion 502 may form distal to theprobe in a substantially spherical shape. In another example, as shownin FIG. 11B, the conductive portion 118 of the probe may extendproximally along the length of the probe for a short distance, forexample between about 2 mm and about 4 mm. In such an embodiment, with asufficient amount of cooling, a lesion 502 may form around theconductive portion as well as distal to the probe. Thus, the degree ofcooling, as well as the probe geometry/configuration and positioning mayeach affect the lesion that may be formed. Because lesions formed bythis method may reach tissue that lies within grooves or otherindentations within a bone, or directly on the surface of a bone, thismethod may be particularly useful for lesioning of the nerves of themedial branch of the dorsal ramus at the cervical region of the spine.

Another application of embodiments of a method of the present inventionis for the treatment of pain in the lumbar region of a patient's spine.With reference now to FIG. 12, the lumbar region generally consists offive vertebrae 1200 and their associated facet joints. The lumbar facetjoints are formed by the superior 1202 and inferior 1204 articularprocesses of successive vertebrae. On the dorsolateral surface of eachsuperior articular facet is a prominence known as the mammillary body orprocess. There is also an accessory process which arises from the dorsalsurface of the transverse process 1206 near its junction with thesuperior articular process. The nerve supply of the lumbar facet jointsis derived from the dorsal primary ramus of the nerve root. Each facetjoint receives innervation from two successive medial branches of thedorsal primary ramus. At the L1-L4 levels, each dorsal ramus arises fromthe spinal nerve at the level of the intervertebral disc. About 5 mmfrom its origin, the dorsal ramus divides into a medial and lateralbranch. The medial branch runs caudally and dorsally, lying against boneat the junction of the root of the transverse process with the root ofthe superior articular process. The medial branch runs medially andcaudally just caudal to the facet joint, and becomes embedded in thefibrous tissue surrounding the joint. The medial branch gives off abranch to each of the proximal and distal facet joint. The proximalfacet nerve supplies the rostra aspect of the next lower joint. Thecourse of the medial branch of the dorsal ramus is fixed anatomically attwo points: at its origin near the superior aspect of the base of thetransverse process, and distally where it emerges from the canal formedby the mammillo-accessory ligament.

A method of treating lumbar pain in accordance with an embodiment of thepresent invention will be presently described. The description willreference the anatomy of the first lumbar vertebra; however persons ofskill in the art will recognize that the method may be used to treatother lumber vertebrae as well. Variations of the described method maybe required in order to accommodate anatomical differences of otherlumbar vertebrae. In some embodiments, the target site for treatinglumbar pain can include the nerves innervating the facet joint. Asdescribed hereinabove, these nerves may be located substantiallyadjacent to the articular process of the lumbar vertebra. Thus thetarget site for energy delivery may be the dorsal surface of thetransverse process just caudal to the most medial end of the superioredge of the transverse process.

In one specific embodiment, the patient may be placed in the proneposition in preparation for the treatment procedure. The user mayoptionally administer various treatments, such as anesthetics orantibiotics, for example. The user may insert at least one probe, suchas probe 100 described hereinabove, percutaneously toward the targetsite. In general, due to the large and controllable lesion size affordedby the structure of probe 100, probe 100 may be inserted from a numberof angles and positioned at a wide variety of locations to create alesion at the target site. The step of inserting at least one probe caninclude the use of an introducer apparatus. Such an apparatus may be anintroducer apparatus comprising the introducer 604 and the obturator606. The user may insert the introducer apparatus percutaneously intothe patient via several different approaches. For example, in oneembodiment, the introducer may be inserted in the sagittal plane of themedial branch one or two levels caudal to the target site, and may beadvanced in a rostral and anterior direction. In another embodiment, theintroducer may be advanced from a more lateral position with obliquemedial angulation. In other embodiments, the probe may be introduced atother sites, and inserted at other angles. The insertion step may befacilitated with the use of fluoroscopic imaging techniques. The usermay continue the insertion until a distal end of the introducerapparatus contacts the dorsal surface of the transverse process justcaudal to the most medial end of the superior edge of the transverseprocess, or may stop the insertion when the distal end lies somedistance, for example about 2 to about 4 millimeters, proximal from thesurface. In other embodiments, the user may contact the surface of thetransverse process with the tip of the introducer, and may then retractthe introducer apparatus such that the distal end lies some distanceproximal from the surface. In some embodiments, the user may use depthstoppers to aid in the marking and/or maintaining the position of theintroducer apparatus within the patient's body.

Depending on the configuration and positioning of the probe, as well thedegree of cooling supplied to the probe, the lesion formed at the targetsite may be of a variety of shapes and sizes, as described above. Forexample, as shown in FIG. 12, in embodiments wherein the conductiveportion 118 of the probe 100 extends proximally along the length of theprobe for a small distance, for example about 2 mm to about 6 mm, forexample about 4 mm, and with a sufficient amount of cooling, a lesion502 may form around the conductive portion as well as distal to theprobe. Because lesions formed by this method may reach tissue that lieswithin grooves or other indentations within a bone or directly on thesurface of a bone, this method may be particularly useful for lesioningof the nerves of the medial branch of the dorsal ramus at the lumbarregion of the spine.

Referring now to FIG. 13, the vertebrae 1300 of the thoracic region areintermediate in size between those of the cervical and lumbar regions,the upper vertebrae being smaller than those in the lower part of theregion. The vertebral bodies are generally as broad in theantero-posterior as in the transverse direction. At the ends of thethoracic region the vertebral bodies resemble respectively those of thecervical and lumbar vertebrae. As shown in FIG. 13, the pedicles of thethoracic vertebrae 1300 are directed backward and slightly upward. Thespinous process 1308 is long and extends posterior and caudal, and endsin a tuberculated extremity. The thoracic facet joints are paired jointslocated between the superior articular process 1302 and inferiorarticular process 1304 of the vertebrae. The superior articularprocesses are thin plates of bone projecting upward from the junctionsof the pedicles and laminae; their articular facets are practicallyflat, and are directed posteriorly and slightly lateral and upward. Theinferior articular processes are fused to a considerable extent with thelaminae, and project slightly beyond their lower borders; their facetsare directed anteriorly and slightly medial and downward. The transverseprocesses 1306 arise from the arch behind the superior articularprocesses and pedicles; they are directed obliquely backward andlateral. The thoracic facet joints are innervated by the medial branchesof the dorsal rami. The medial branches pass between consecutivetransverse processes and head medially and inferiorly. They theninnervate the facet joint at the level of their spinal nerve and thejoint below. At T1-3 and T9-10, the medial branches cross thesuperior-lateral aspect of the transverse process. At T4-8, the medialbranches follow a similar course, but may remain suspended within theintertransverse space. At T11-12, the medial branch has a course akin tothe lumbar medial branches such that they course posteriorly along themedial aspect of the transverse process, at the root of the superiorarticular process.

Due to the varied course of the medial branch across the twelve thoraciclevels, the lack of bony landmarks associated with the thoracic medialbranch, and the anatomic differences among patients, it is oftenrequired to create several lesions in order to denervate one thoracicfacet joint. Embodiments of the present invention may allow for theformation of a single large lesion for the denervation of a facet joint,for example by using cooling, thus providing a more straightforward andless invasive procedure.

A method of treating thoracic pain in accordance with an embodiment ofthe present invention will be presently described. The description willreference the anatomy of the first through tenth thoracic vertebrae.Variations of the described method may be required in order toaccommodate anatomical differences of other thoracic vertebrae. In someembodiments, the target site for treating thoracic pain can include thenerves innervating the facet joint. As described hereinabove, thesenerves may be located substantially laterally between two consecutivetransverse processes, or substantially adjacent the superior edge of atransverse process. Thus the target site 1310 for energy delivery may bethe superior lateral edge of the transverse process and the regionimmediately superior thereto.

In one specific embodiment, the patient may be placed in the proneposition in preparation for the treatment procedure. The user mayoptionally administer various treatments, such as anesthetics orantibiotics, for example. The user may insert at least one probe, suchas the probe 100 described hereinabove, percutaneously toward the targetsite. In general, due to the large and controllable lesion size affordedby the structure of the probe 100, the probe 100 may be inserted from anumber of angles and positioned at a wide variety of locations to createa lesion at the target site. The step of inserting at least one probecan include the use of an introducer apparatus. Such an apparatus may bean introducer apparatus comprising the introducer 604 and the obturator606.

The user may insert the introducer apparatus percutaneously into thepatient via several different approaches. For example, as shown in FIG.14, in one embodiment, the introducer may be inserted slightly medial tothe lateral edge of the transverse process 1306, and advanced in theanterior direction. In another embodiment, the introducer may beadvanced from a more medial position with oblique lateral angulation. Inother embodiments, the probe may be introduced at other sites, andinserted at other angles. In some embodiments, the insertion step may befacilitated with the use of fluoroscopic imaging techniques. The usermay continue the insertion until a distal end of the introducerapparatus contacts the transverse process 1306. The user may then “walk”the introducer apparatus in the cranial direction, until the distal endof the introducer begins to slip over the superior edge of thetransverse process 1306. The user may then withdraw the introducerslightly, such that the distal end of the introducer is substantiallyabove the superior lateral edge of transverse process 1306. In someembodiments, the user may use depth stoppers to aid in the markingand/or maintaining the position of the introducer apparatus within thepatient's body.

Depending, for example, on the configuration and positioning of theprobe, as well as the degree of cooling supplied to the probe, thelesion formed at the target site may be of a variety of shapes andsizes, as described hereinabove. For example, as shown in FIG. 14, inembodiments wherein the conductive portion 118 of the probe 100 extendsproximally along the length of the probe for a small distance, forexample between about 1 mm and about 4 mm, and with a sufficient amountof cooling, for example between about 10 ml/min and about 25 ml/min, alesion 502 may form around the conductive portion as well as distal tothe probe. Because lesions formed by this method may be substantiallylarge, for example between about 150 mm³ and about 500 mm³ in volume,this method may be particularly useful for lesioning of the nerves ofthe medial branch of the dorsal ramus at the thoracic region of thespine.

A further application of embodiments of the apparatus and method of thepresent invention is for the treatment of pain emanating from theSacroiliac (SI) joint and/or the surrounding region. Some detailsregarding such a treatment procedure are disclosed in U.S. Pat. No.7,819,869 to Godara, et al. and U.S. Pat. No. 8,951,249 to Godara, etal., which are incorporated herein by reference. The SI joint 1500 isthe joint between the sacrum 1502, a large bone at the base of the spinecomposed of five fused vertebrae, and the ilium 1504 of the pelvis. TheSI joint is a relatively immobile joint, serving to absorb shock duringlocomotion. The structure of the SI joint and surrounding tissues variessignificantly between individuals but generally includes an articularcartilaginous surface, a ligamentous aspect and, in most cases, one ormore synovial recesses. Though the specific pathways of SI jointinnervation have not yet been elucidated, the nerves responsible for SIpain are thought to include, at least in part, nerves emanating from thedorsal sacral plexus, the network of nerves on the posterior surface ofthe sacrum, extending from the sacral nerves, also referred to as theposterior primary rami 1506, that exit the sacral foramina 1508(posterior sacral foramen). The lateral branches 1510 branch out fromthe sacral nerves (and branch out further along the sacrum as well) andare thought to play a role in the innervation of the SI joint. Thesurface of the sacrum can be very uneven, inhibiting the ability of asmall lesion to affect nerves running along crests of the sacrum, aswell as those within the grooves or recesses in the sacral surface;furthermore, accessing the sacrum can require penetrating the sacroiliacligaments, ligaments responsible for bearing a large proportion of theweight of the body and which, desirably, would be severed or weakened aslittle as possible.

Due to the anatomy of the sacrum, a straight “gun-barrel” approach,substantially perpendicular to the plane of the sacrum or to the targetsite, may be desirable. However, if a target nerve to be lesioned isrunning through a narrow groove or fissure that is too narrow toaccommodate a probe capable of creating a lesion with the desiredvolume, the nerve may remain distal to an inserted probe, even if theprobe is in contact with the surface of the sacrum. Embodiments of thedevice of the present invention may be used according to embodiments ofthe method described above in order to create a lesion that is primarilylocated distal to the probe 100. This may allow for a substantiallyperpendicular “gun-barrel” approach and a lesion thus created mayencompass the target nerve.

In some embodiments, it may be desired to treat one or more neuralstructures within a sacral neural crescent. The term “sacral neuralcrescent” refers to an area lateral to each of the sacral foramina,through which the sacral nerves are believed to pass after exiting theforamina. On the dorsal right side of the sacrum, this window is fromabout 12 o'clock to about 6 o'clock in a clockwise direction, while onthe dorsal left side of the sacrum the window is from about 6 o'clock toabout 12 o'clock in a clockwise direction. Similar (but in thecounter-clockwise direction) areas exist on the ventral side of thesacrum. The clock positions are referenced as if the foramen is viewedas a clock face, and the view is taken looking towards the sacrum. Forreference, the 12 o'clock position of the clock face would be the mostcephalad (towards the head) point of the foramen.

In other embodiments, methods of the present invention may be used totreat other conditions at various regions within the body, which may beexternal to the patient's spine. Examples of such conditions include,but are not limited to, pain-causing conditions such as Complex RegionalPain Syndrome (CRPS), Trigeminal Neuralgia, Joint Specific PeripheralNeuropathy, Facet Joint Pain, Fibrotic pain or pain due to scar tissue,and Hypogastric or Pelvic Pain. In general, these conditions may betreated by lesioning at least one target nerve that may be associatedwith a patient's pain in accordance with method embodiments of thepresent invention. For example, in the case of trigeminal neuralgia,devices and methods of the present invention may be used to form alesion at the trigeminal nerve. In the case of CRPS, devices and methodsof the present invention may be used to form a lesion at a sympatheticnerve chain.

In addition to the treatment of pain-causing conditions, methods anddevices of the present invention may be used for other applications,such as cardiac ablation, for example in cases of atrial tachycardia, isremoval or treatment of scar tissue, treatment of varicose veins,treatment of hyperparathyroidism, and ablation of malignancies ortumors, for example in the lung, liver, or bone. In general, theseconditions may be treated by lesioning at least one target siteassociated with a symptom or cause of a patient's condition. Forexample, in the case of atrial tachycardia, devices and methods of thepresent invention may be used to form a lesion at the His Bundle regionof the heart. In the case of hyperparathyroidism, devices and methods ofthe present invention may be used to form a lesion at one or moreparathyroid glands.

The embodiments of the invention described above are intended to beexemplary only. The scope of the invention is therefore intended to belimited solely by the scope of the appended claims.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims. All publications, patents and patentapplications mentioned in this specification are herein incorporated intheir entirety by reference into the specification, to the same extentas if each individual publication, patent or patent application wasspecifically and individually indicated to be incorporated herein byreference. In addition, citation or identification of any reference inthis application shall not be construed as an admission that suchreference is available as prior art to the present invention.

1. An electrosurgical device comprising: a probe extending in alongitudinal direction, wherein the probe includes a proximal region anda distal region, wherein an inner diameter of the probe defines a lumen,wherein the probe has an electrically insulated portion extending fromthe proximal region to the distal region and an electrically exposedconductive portion located at the distal region, wherein theelectrically exposed conductive portion delivers radiofrequency energyto an area of tissue adjacent the distal region of the probe; and a heattransfer system for removing thermal energy from the area of tissue,wherein the heat transfer system is in thermal contact with the area oftissue, wherein the heat transfer system removes from about 0.1 Watts toabout 50 Watts of energy from the area of tissue.
 2. The electrosurgicaldevice of claim 1, wherein the heat transfer system removes from about 2Watts to about 12 Watts of energy from the area of tissue.
 3. Theelectrosurgical device of claim 1, wherein the heat transfer system isat least partially disposed within the lumen.
 4. The electrosurgicaldevice of claim 1, wherein the heat transfer system is configured toabsorb or remove thermal energy over a time period ranging from about 60seconds to about 300 seconds.
 5. The electrosurgical device of claim 1,wherein the heat transfer system comprises a heat removal material inthermal contact with the area of tissue.
 6. The electrosurgical deviceof claim 5, wherein the heat removal material is disposed within thelumen.
 7. The electrosurgical device of claim 5, wherein the heatremoval material is positioned on an exterior surface of the probe, anintroducer, or a combination thereof.
 8. The electrosurgical device ofclaim 5, wherein the heat removal material comprises a heat transfermaterial, a heat sink, or a combination thereof.
 9. The electrosurgicaldevice of claim 8, wherein the heat transfer material comprises athermally conductive material, one or more Peltier circuits, or acombination thereof.
 10. The electrosurgical device of claim 9, whereinthe thermally conductive material comprises a metal, a ceramic material,a conductive polymer, or a combination thereof.
 11. The electrosurgicaldevice of claim 10, wherein the metal comprises a silver paste.
 12. Theelectrosurgical device of claim 9, wherein the one or more Peltiercircuits are positioned within a hub of the electrosurgical device, ahandle of the electrosurgical device, the distal region of the probe,the proximal region of the probe, or a combination thereof, wherein aconnection exists between the one or more Peltier circuits and thedistal region of the probe.
 13. The electrosurgical device of claim 12,wherein each Peltier circuit includes a hot side and a cold side,wherein the hot side faces the proximal region of the probe and the coldside faces the distal region of the probe.
 14. The electrosurgicaldevice of claim 8, wherein the heat sink comprises a phase changematerial.
 15. The electrosurgical device of claim 14, wherein the phasechange material changes phase at a temperature between about 40° C. and100° C.
 16. The electrosurgical device of claim 14, wherein the phasechange material has a heat of fusion ranging from about 150 Joules/gramto about 300 Joules/gram.
 17. The electrosurgical device of claim 14,wherein from about 1 gram to about 12 grams of the phase change materialis required to remove from about 2 Watts to about 12 Watts of energyfrom the probe over a 150 second time period.
 18. The electrosurgicaldevice of claim 14, to 17, wherein the phase change material comprises aparaffin wax.
 19. The electrosurgical device of claim 14, wherein thephase change material surrounds a conductor extending from theelectrically exposed conductive portion of the probe at the distalregion of the probe towards a proximal end of the probe.
 20. Theelectrosurgical device of claim 8, wherein the heat sink comprises a gasor a pressurized liquid, wherein the gas or the pressurized liquid iscontained within the lumen.
 21. The electrosurgical device of claim 20,wherein the gas is carbon dioxide or nitrogen and the liquid is liquidcarbon dioxide.
 22. The electrosurgical device of claim 20, wherein thelumen contains an inlet channel, wherein the gas or pressurized liquidis introduced into the lumen, and an outlet channel where the gas orpressurized liquid exits the lumen, wherein the inlet channel and theoutlet channel are defined by a separator, wherein the inlet channel hasa diameter that is smaller than a diameter of the outlet channel. 23.The electrosurgical device of claim 8, wherein the heat sink comprisesan endothermic reaction system, wherein the endothermic reaction systemcomprises a first material separated from a second material, wherein anendothermic reaction occurs when the first material contacts the secondmaterial.
 24. The electrosurgical device of claim 23, wherein the firstmaterial comprises water and the second material comprises ammoniumnitrate.
 25. The electrosurgical device of claim 24, wherein the firstmaterial and the second material are stored in a cartridge that isinserted into the lumen prior to use of the electrosurgical device. 26.The electrosurgical device of claim 23, wherein the heat transfer systemfurther comprises a wire, wherein the wire facilitates the transfer ofheat from the electrically exposed conductive portion of the probe tothe endothermic reaction between the first material and the secondmaterial.
 27. The electrosurgical device of claim 8, wherein the heatremoval material includes the heat transfer material and the heat sink,wherein the heat transfer material is in thermal communication with theheat sink.
 28. The electrosurgical device of claim 27, wherein the heatsink is an external heat sink.
 29. The electrosurgical device of claim27, wherein the heat transfer material is in communication with the heatsink via one or more conductive wires or conduits.
 30. Theelectrosurgical device of claim 8, wherein the heat sink comprises aseries of fins, etchings, particulates, or a combination thereof. 31.The electrosurgical device of claim 1, wherein the area of tissueadjacent the distal region of the probe is maintained at a temperatureof less than about 90° C.
 32. The electrosurgical device of claim 1,wherein the heat transfer system is free of a circulating liquid, 33.The electrosurgical device of claim 1, wherein the heat transfer systemis free of a pump.